Grating waveguide combiner for optical engine

ABSTRACT

Systems, devices, and methods of manufacturing optical engines and laser projectors that are well-suited for use in wearable heads-up displays (WHUDs) are described. Generally, the optical engines of the present disclosure integrate a plurality of laser diodes (e.g., 3 laser diodes, 4 laser diodes) within a single, hermetically or partially hermetically sealed, encapsulated package. A grating waveguide combiner comprising a plurality of waveguides having grating couplers thereon may be used to combine beams of light emitted by the plurality of laser diodes into a coaxially superimposed aggregate beam. Such optical engines may have advantages over existing designs including, for example, smaller volumes, better manufacturability, faster modulation speed, etc. WHUDs that employ such optical engines and laser projectors are also described.

BACKGROUND Technical Field

The present disclosure is generally directed to systems, devices, andmethods relating to optical engines, for example, optical engines forlaser projectors used in wearable heads-up displays or otherapplications.

Description of the Related Art

A projector is an optical device that projects or shines a pattern oflight onto another object (e.g., onto a surface of another object, suchas onto a projection screen) in order to display an image or video onthat other object. A projector necessarily includes a light source, anda laser projector is a projector for which the light source comprises atleast one laser. The at least one laser is temporally modulated toprovide a pattern of laser light and usually at least one controllablemirror is used to spatially distribute the modulated pattern of laserlight over a two-dimensional area of another object. The spatialdistribution of the modulated pattern of laser light produces an imageat or on the other object. In conventional scanning laser projectors, atleast one controllable mirror may be used to control the spatialdistribution, and may include: a single digital micromirror (e.g., amicroelectromechanical system (“MEMS”) based digital micromirror) thatis controllably rotatable or deformable in two dimensions, or twodigital micromirrors that are each controllably rotatable or deformableabout a respective dimension, or a digital light processing (“DLP”) chipcomprising an array of digital micromirrors.

In a conventional laser projector comprising an RGB (red/green/blue)laser module with a red laser diode, a green laser diode, and a bluelaser diode, each respective laser diode may have a correspondingrespective focusing lens. Each of the laser diodes of a laser module aretypically housed in a separate package (e.g., a TO-38 package or “can”).The relative positions of the laser diodes, the focusing lenses, and theat least one controllable mirror are all tuned and aligned so that eachlaser beam impinges on the at least one controllable mirror withsubstantially the same spot size and with substantially the same rate ofconvergence (so that all laser beams will continue to have substantiallythe same spot size as they propagate away from the laser projectortowards, e.g., a projection screen). In a conventional laser projector,it is usually possible to come up with such a configuration for allthese elements because the overall form factor of the device is not aprimary design consideration. However, in applications for which theform factor of the laser projector is an important design element, itcan be very challenging to find a configuration for the laser diodes,the focusing lenses, and the at least one controllable mirror thatsufficiently aligns the laser beams (at least in terms of spot size,spot position, and rate of convergence) while satisfying the form factorconstraints.

A head-mounted display is an electronic device that is worn on a user'shead and, when so worn, secures at least one electronic display within aviewable field of at least one of the user's eyes, regardless of theposition or orientation of the user's head. A wearable heads-up displayis a head-mounted display that enables the user to see displayed contentbut also does not prevent the user from being able to see their externalenvironment. The “display” component of a wearable heads-up display iseither transparent or at a periphery of the user's field of view so thatit does not completely block the user from being able to see theirexternal environment. A “combiner” component of a wearable heads-updisplay is the physical structure where display light and environmentallight merge as one within the user's field of view. The combiner of awearable heads-up display is typically transparent to environmentallight but includes some optical routing mechanism to direct displaylight into the user's field of view.

Examples of wearable heads-up displays include: the Google Glass®, theOptinvent Ora®, the Epson Moverio®, and the Sony Glasstron®, just toname a few.

The optical performance of a wearable heads-up display is an importantfactor in its design. When it comes to face-worn devices, users alsocare a lot about aesthetics and comfort. This is clearly highlighted bythe immensity of the eyeglass (including sunglass) frame industry.Independent of their performance limitations, many of the aforementionedexamples of wearable heads-up displays have struggled to find tractionin consumer markets because, at least in part, they lack fashion appealor comfort. Most wearable heads-up displays presented to date employrelatively large components and, as a result, are considerably bulkier,less comfortable and less stylish than conventional eyeglass frames.

Direct Laser Writing

Femtosecond laser micro-machining is a direct-laser-write and rapidprototyping technique that provides great potential for optical devicefabrication. Strong focusing of femtosecond laser light into transparentglass can induce positive refractive index modifications up to 0.01refractive index units (MU) within the material and without surfacedamage. Since then, ultrafast (femto/pico-second) lasers have been shownto enable flexible 3D structuring of various glasses, and has led to thedemonstration of many types of optical devices (waveguides, couplers,Bragg gratings, waveplates, etc.) that serve as building blocks for 3Doptical circuits.

Direct-laser-writing uses ultrashort laser pulses to confine strongnonlinear optical interactions that may induce, for example, positive ornegative refractive index changes in bulk transparent materials forcreating optical waveguides (WGs). The mechanisms by whichdirect-laser-write modifications occur include, but are not limited to,multiphoton ionization, avalanche ionization, electron-atom collisions,plasma interactions, thermal effects (e.g. diffusion, heataccumulation), energy dissipation, and material cooling leading toinhomogeneous solidification. For direct-laser-writing waveguides,waveguide performance can be tuned and optimized by, but not limited to,the writing laser's properties (pulse duration, pulse temporal shape,bandwidth and shape, pulse repetition rate, wavelength, polarization,and beam spatial shape) and the focusing conditions (lens numericalaperture, air/liquid immersion, translation direction and speeds).

BRIEF SUMMARY

According to one or more implementations of the present disclosure, anoptical engine may be summarized as including: a base substrate; aplurality of laser diodes, each of the plurality of laser diodes bondeddirectly or indirectly to the base substrate; at least one laser diodedriver circuit operatively coupled to the plurality of laser diodes toselectively drive current to the plurality of laser diodes; a pluralityof collimation lenses, each of the plurality of collimation lensespositioned proximate a respective one of the plurality of laser diodescollimates light emitted therefrom; a cap comprising at least one walland at least one optical window that, together with the base substrate,define an interior volume sized and dimensioned to receive at least theplurality of laser diodes and the plurality of collimation lenses, thecap being bonded to the base substrate to provide a hermetic orpartially hermetic seal between the interior volume of the cap and avolume exterior to the cap, and the optical window positioned andoriented to allow beams of light emitted from the plurality of laserdiodes through the collimation lenses to exit the interior volume; and agrating waveguide combiner positioned proximate the optical window ofthe cap, the grating waveguide combiner comprising a plurality of inputgrating couplers and at least one output grating coupler, in operation,the grating waveguide combiner receives a plurality of beams of light atthe respective plurality of input grating couplers and combines theplurality of beams of light to provide a collimated aggregated beam oflight at the output grating coupler.

The grating waveguide combiner may include a first grating waveguide anda second grating waveguide. Each of the first and second gratingwaveguides may include at least two input grating couplers. The gratingwaveguide combiner may include at least four waveguides. The pluralityof collimation lenses may be formed as a micro-optic lens array. Theplurality of collimation lenses may be bonded to the base substrate. Thegrating waveguide combiner may be bonded to the base substrate proximatethe optical window of the cap.

The optical engine may further include a common collimation lenspositioned and oriented to receive and collimate the aggregate beam oflight from the output grating coupler of the grating waveguide combiner.The common collimation lens may include an achromatic lens or anapochromatic lens.

The optical engine may further include at least one diffractive opticalelement positioned and oriented to receive the aggregate beam of light,in operation, the at least one diffractive optical element may providewavelength dependent focus correction for the aggregate beam of light.

The optical engine may further include a plurality of chip submountsbonded to the base substrate, wherein each of the laser diodes arebonded to a corresponding one of the plurality of chip submounts. Theplurality of laser diodes may include a red laser diode to provide a redlaser light, a green laser diode to provide a green laser light, a bluelaser diode to provide a blue laser light, and an infrared laser diodeto provide infrared laser light. The base substrate may be formed fromat least one of low temperature co-fired ceramic (LTCC), aluminumnitride (A1N), or alumina.

The at least one laser diode driver circuit may be bonded to a firstsurface of the base substrate, and the plurality of laser diodes and thecap may be bonded to a second surface of the base substrate, the secondsurface of the base substrate opposite the first surface of the basesubstrate. The at least one laser diode driver circuit, the plurality oflaser diodes, and the cap may be bonded to a first surface of the basesubstrate. The plurality of laser diodes and the cap may be bonded tothe base substrate, and the at least one laser diode driver circuit maybe bonded to another substrate separate from the base substrate.

Each of the laser diodes may include one of an edge emitter laser or avertical-cavity surface-emitting laser (VCSEL).

According to one or more implementations of the present disclosure, alaser projector may be summarized as including: an optical engine,comprising: a base substrate; a plurality of laser diodes, each of theplurality of laser diodes bonded directly or indirectly to the basesubstrate; at least one laser diode driver circuit operatively coupledto the plurality of laser diodes to selectively drive current to theplurality of laser diodes; a plurality of collimation lenses, each ofthe plurality of collimation lenses positioned proximate a respectiveone of the plurality of laser diodes collimates light emitted therefrom;a cap comprising at least one wall and at least one optical window that,together with the base substrate, define an interior volume sized anddimensioned to receive at least the plurality of laser diodes and theplurality of collimation lenses, the cap being bonded to the basesubstrate to provide a hermetic or partially hermetic seal between theinterior volume of the cap and a volume exterior to the cap, and theoptical window positioned and oriented to allow beams of light emittedfrom the plurality of laser diodes through the collimation lenses toexit the interior volume; and a grating waveguide combiner positionedproximate the optical window of the cap, the grating waveguide combinercomprising a plurality of input grating couplers and at least one outputgrating coupler, in operation, the grating waveguide combiner receives aplurality of beams of light at the respective plurality of input gratingcouplers and combines the plurality of beams of light to provide acollimated aggregated beam of light at the output grating coupler; andat least one scan mirror positioned to receive the aggregate beam oflight output at the output grating coupler of the grating waveguidecombiner, the at least one scan mirror controllably orientable toredirect the aggregate beam of light over a range of angles.

The grating waveguide combiner may include a first grating waveguide anda second grating waveguide. Each of the first and second gratingwaveguides may include at least two input grating couplers. The gratingwaveguide combiner may include at least four waveguides.

The plurality of collimation lenses may be formed as a micro-optic lensarray. The plurality of collimation lenses may be bonded to the basesubstrate. The grating waveguide combiner may be bonded to the basesubstrate proximate the optical window of the cap.

The optical engine of the laser projector may further include a commoncollimation lens positioned and oriented to receive and collimate theaggregate beam of light from the output grating coupler of the gratingwaveguide combiner. The common collimation lens may include anachromatic lens. The common collimation lens may include an apochromaticlens.

The optical engine of the laser projector may further comprise at leastone diffractive optical element positioned and oriented to receive theaggregate beam of light, in operation, the at least one diffractiveoptical element may provide wavelength dependent focus correction forthe aggregate beam of light.

The optical engine of the laser projector may further include aplurality of chip submounts bonded to the base substrate, wherein eachof the laser diodes are bonded to a corresponding one of the pluralityof chip submounts. The plurality of laser diodes may include a red laserdiode to provide a red laser light, a green laser diode to provide agreen laser light, a blue laser diode to provide a blue laser light, andan infrared laser diode to provide infrared laser light. The basesubstrate may be formed from at least one of low temperature co-firedceramic (LTCC), aluminum nitride (A1N), or alumina.

The at least one laser diode driver circuit may be bonded to a firstsurface of the base substrate, and the plurality of laser diodes and thecap may be bonded to a second surface of the base substrate, the secondsurface of the base substrate opposite the first surface of the basesubstrate. The at least one laser diode driver circuit, the plurality oflaser diodes, and the cap may be bonded to a first surface of the basesubstrate. The plurality of laser diodes and the cap may be bonded tothe base substrate, and the at least one laser diode driver circuit maybe bonded to another substrate separate from the base substrate. Each ofthe laser diodes may be one of an edge emitter laser or avertical-cavity surface-emitting laser (VCSEL).

According to one or more implementations of the present disclosure, awearable heads-up display (WHUD) may be summarized as including: asupport structure that in use is worn on the head of a user; a laserprojector carried by the support structure, the laser projectorcomprising: an optical engine, comprising: a base substrate; a pluralityof laser diodes, each of the plurality of laser diodes bonded directlyor indirectly to the base substrate; at least one laser diode drivercircuit operatively coupled to the plurality of laser diodes toselectively drive current to the plurality of laser diodes; a pluralityof collimation lenses, each of the plurality of collimation lensespositioned proximate a respective one of the plurality of laser diodescollimates light emitted therefrom; a cap comprising at least one walland at least one optical window that, together with the base substrate,define an interior volume sized and dimensioned to receive at least theplurality of laser diodes and the plurality of collimation lenses, thecap being bonded to the base substrate to provide a hermetic orpartially hermetic seal between the interior volume of the cap and avolume exterior to the cap, and the optical window positioned andoriented to allow beams of light emitted from the plurality of laserdiodes through the collimation lenses to exit the interior volume; and agrating waveguide combiner positioned proximate the optical window ofthe cap, the grating waveguide combiner comprising a plurality of inputgrating couplers and at least one output grating coupler, in operation,the grating waveguide combiner receives a plurality of beams of light atthe respective plurality of input grating couplers and combines theplurality of beams of light to provide a collimated aggregated beam oflight at the output grating coupler; and at least one scan mirrorpositioned to receive the aggregate beam of light output at the outputgrating coupler of the grating waveguide combiner, the at least one scanmirror controllably orientable to redirect the aggregate beam of lightover a range of angles.

The grating waveguide combiner may include a first grating waveguide anda second grating waveguide. Each of the first and second gratingwaveguides may include at least two input grating couplers. The gratingwaveguide combiner may include at least four waveguides.

The plurality of collimation lenses may be formed as a micro-optic lensarray. The plurality of collimation lenses may be bonded to the basesubstrate. The grating waveguide combiner may be bonded to the basesubstrate proximate the optical window of the cap.

The optical engine of the laser projector may further include a commoncollimation lens positioned and oriented to receive and collimate theaggregate beam of light from the output grating coupler of the gratingwaveguide combiner. The common collimation lens may include anachromatic lens or an apochromatic lens.

The optical engine of the laser projector may further comprise at leastone diffractive optical element positioned and oriented to receive theaggregate beam of light, in operation, the at least one diffractiveoptical element may provide wavelength dependent focus correction forthe aggregate beam of light.

The optical engine of the laser projector may further include aplurality of chip submounts bonded to the base substrate, wherein eachof the laser diodes are bonded to a corresponding one of the pluralityof chip submounts. The plurality of laser diodes may include a red laserdiode to provide a red laser light, a green laser diode to provide agreen laser light, a blue laser diode to provide a blue laser light, andan infrared laser diode to provide infrared laser light. The basesubstrate may be formed from at least one of low temperature co-firedceramic (LTCC), aluminum nitride (A1N), or alumina.

The at least one laser diode driver circuit may be bonded to a firstsurface of the base substrate, and the plurality of laser diodes and thecap may be bonded to a second surface of the base substrate, the secondsurface of the base substrate opposite the first surface of the basesubstrate. The at least one laser diode driver circuit, the plurality oflaser diodes, and the cap may be bonded to a first surface of the basesubstrate. The plurality of laser diodes and the cap may be bonded tothe base substrate, and the at least one laser diode driver circuit maybe bonded to another substrate separate from the base substrate. Theplurality of laser diodes and the cap may be bonded to the basesubstrate, and the at least one laser diode driver circuit may bemounted to the support structure of the WHUD.

Each of the laser diodes may be one of an edge emitter laser or avertical-cavity surface-emitting laser (VCSEL). The WHUD may furtherinclude a processor communicatively coupled to the laser projector tomodulate the generation of light signals. The WHUD may further include atransparent combiner carried by the support structure and positionedwithin a field of view of the user, in operation the transparentcombiner directs laser light from an output of the laser projector intothe field of view of the user.

According to one or more implementations of the present disclosure, amethod of manufacturing an optical engine may be summarized asincluding: bonding a plurality of laser diodes directly or indirectly toa base substrate; coupling at least one laser diode driver circuit tothe laser diodes, in operation the at least one laser diode drivercircuit selectively drives current to the laser diodes; bonding aplurality of collimation lenses to the base substrate proximate theplurality of laser diodes; bonding a cap comprising at least one walland at least one optical window to the base substrate, the at least onewall, the at least one optical window, and at least a portion of thebase substrate together delimit an interior volume sized and dimensionedto receive at least the plurality of laser diodes and the plurality ofcollimation lenses, the bonding of the cap to the base substrateproviding a hermetic or partially hermetic seal between the interiorvolume of the cap and a volume exterior to the cap, and the opticalwindow positioned and oriented to allow light emitted from the laserdiodes through the collimation lenses to exit the interior volume; andbonding a grating waveguide combiner proximate the optical window of thecap, the grating waveguide combiner comprising a plurality of inputgrating couplers and at least one output grating coupler, in operation,the grating waveguide combiner receives a plurality of beams of light atthe respective plurality of input grating couplers and combines theplurality of beams of light to provide a collimated aggregated beam oflight at the output grating coupler.

Bonding a plurality of collimation lenses to the base substrate mayinclude bonding a micro-optic lens array to the base substrate. Themethod may further include actively or passively aligning thecollimation lenses.

Bonding a grating waveguide combiner proximate the optical window of thecap may include writing the plurality of input grating couplers and atleast one output grating coupler into a waveguide medium, andsubsequently bonding the waveguide medium proximate the optical windowof the cap. Bonding a grating waveguide combiner proximate the opticalwindow of the cap may include bonding a writeable waveguide mediumproximate the optical window of the cap, and subsequently writing theplurality of input grating couplers and at least one output gratingcoupler into the waveguide medium.

The method may further include: bonding each of the laser diodesindirectly to the base substrate by bonding each laser diode to arespective chip submount; and bonding each chip submount to the basesubstrate. Bonding each laser diode to a respective chip submount mayinclude bonding each laser diode to a respective chip submount using aeutectic gold tin (AuSn) solder process. Bonding each chip submount tothe base substrate may include step-soldering each chip submount to thebase substrate. Bonding each chip submount to the base substrate mayinclude bonding each chip submount to the base substrate using at leastone of a reflow oven process, thermosonic bonding, thermocompressionbonding, transient liquid phase (TLP) bonding, or laser soldering.Bonding each chip submount to the base substrate may include bonding achip submount that has a red laser diode bonded thereto, bonding a chipsubmount that has a green laser diode bonded thereto, bonding a chipsubmount that has a blue laser diode bonded thereto, and bonding a chipsubmount that has an infrared laser diode bonded thereto.

Coupling at least one laser diode driver circuit to the laser diodes mayinclude: bonding a plurality of electrical connections to the basesubstrate, each electrical connection coupled to a respective laserdiode in the plurality of laser diodes; providing a coupling betweeneach of the plurality of electrical connections and the at least onelaser diode driver circuit; and bonding an electrically insulating coverto the base substrate over the plurality of electrical connections, andbonding the cap to the base substrate may include bonding the cap to thebase substrate and the electrically insulating cover. Providing acoupling between each of the plurality of electrical connections and theat least one laser diode driver circuit may include: bonding a pluralityof electrical contacts to the base substrate, each electrical contactcoupled to a respective one of the plurality of electrical connections;and providing a coupling between each of the electrical contacts and theat least one laser diode driver circuit.

Bonding the plurality of laser diodes directly or indirectly to a basesubstrate may include bonding the laser diodes directly or indirectly toa first surface of the base substrate, and bonding a cap to the basesubstrate may include bonding a cap to the first surface of the basesubstrate, and the method may further include bonding the at least onelaser diode driver circuit to a second surface of the base substrate,the second surface of the base substrate opposite the first surface ofthe base substrate. Bonding the plurality of laser diodes directly orindirectly to a base substrate may include bonding the laser diodesdirectly or indirectly to a first surface of the base substrate, andbonding a cap to the base substrate may include bonding a cap to thefirst surface of the base substrate, and the method may further includebonding the at least one laser diode driver circuit to the first surfaceof the base substrate. Bonding a cap to the base substrate may includebonding a cap to the base substrate using at least one of a seam weldingprocess, a laser assisted soldering process, or a diffusion bondingprocess.

The method may further include positioning and orienting a collimationlens to receive and collimate the aggregate beam of light from theoutput facet of the photonic integrated circuit.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not necessarily drawn to scale, and some ofthese elements may be arbitrarily enlarged and positioned to improvedrawing legibility. Further, the particular shapes of the elements asdrawn, are not necessarily intended to convey any information regardingthe actual shape of the particular elements, and may have been solelyselected for ease of recognition in the drawings.

FIG. 1A is a left side, sectional elevational view of an optical engine,in accordance with the present systems, devices, and methods.

FIG. 1B is a front side, sectional elevational view of the opticalengine also shown in FIG. 1A, in accordance with the present systems,devices, and methods.

FIG. 2 is a flow diagram of a method of operating an optical engine, inaccordance with the present systems, devices, and methods.

FIG. 3 is a schematic diagram of a wearable heads-up display with alaser projector that includes an optical engine, and a transparentcombiner in a field of view of an eye of a user, in accordance with thepresent systems, devices, and methods.

FIG. 4 is an isometric view of a wearable heads-up display with a laserprojector that includes an optical engine, in accordance with thepresent systems, devices, and methods.

FIG. 5 is a flow diagram of a method of manufacturing an optical engine,in accordance with the present systems, devices, and methods.

FIG. 6 is a top plan view of a photonic integrated circuit forwavelength multiplexing that includes a plurality of grating couplers ona surface thereof, the photonic integrated circuit followed by a commoncollimation lens and an optional diffractive optical element, inaccordance with the present systems, devices, and methods.

FIG. 7 is a left side sectional elevational view of an optical enginethat includes a plurality of laser diodes inside a hermetically orpartially hermetically sealed package coupled to the photonic integratedcircuit of FIG. 6 for wavelength multiplexing, and a common collimationlens and an optional diffractive optical element, in accordance with thepresent systems, devices, and methods.

FIG. 8 is a top plan view of a photonic integrated circuit forwavelength multiplexing followed by a common collimation lens and anoptional diffractive optical element, in accordance with the presentsystems, devices, and methods.

FIG. 9 is a left side sectional elevational view of an optical enginethat includes a plurality of laser diodes inside a hermetically orpartially hermetically sealed package coupled to a photonic integratedcircuit of FIG. 8 for wavelength multiplexing, and a common collimationlens and an optional diffractive optical element, in accordance with thepresent systems, devices, and methods.

FIG. 10 is a schematic diagram of a laser writing system which can beused to write photonic integrated circuits in accordance with thepresent systems, devices, and methods.

FIG. 11 is a flow diagram of a method of manufacturing an optical engineincluding writing a photonic integrated circuit, in accordance with thepresent systems, devices, and methods.

FIGS. 12A, 12B, and 13 are schematic diagrams of laser writing systemswhich can be used to write photonic integrated circuits in writeableglass already bonded to a substrate or circuit, according to at leasttwo illustrated implementations.

FIG. 14 is a left side sectional elevational view of an optical enginethat includes a plurality of laser diodes inside a hermetically orpartially hermetically sealed package coupled to a photonic integratedcircuit for wavelength multiplexing via a directly written waveguide, inaccordance with the present systems, devices, and methods.

FIG. 15 is a left side sectional elevational view of an optical enginethat includes a plurality of laser diodes coupled to a photonicintegrated circuit for wavelength multiplexing via a directly writtenwaveguide, wherein the waveguide is formed in a waveguide medium thatalso provides a hermetic or partially hermetic seal for the plurality oflaser diodes, in accordance with the present systems, devices, andmethods.

FIGS. 16A and 16B are isometric views of optical engines including aninsulating cover which prevents undesired electrical signal transmissionfrom electrical connections, and showing implementations of opticalengines having differing positions for a laser diode driver circuit inaccordance with the present systems, devices, and methods.

FIG. 17A is a left side sectional elevational view of an optical enginethat includes a plurality of laser diodes inside a hermetically sealedpackage, and further includes a grating waveguide combiner that inputslight emitted from the plurality of laser diodes and outputs asuperimposed collimated beam, in accordance with the present systems,devices, and methods.

FIG. 17B is a front side elevational view of the optical engine of FIG.17A, in accordance with the present systems, devices, and methods.

FIG. 18 is an isometric view of a laser diode, showing a fast axis and aslow axis of a light beam generated by the laser diode, in accordancewith the present systems, devices, and methods.

FIG. 19A is a left side sectional view of a set of collimation lensesfor collimating a beam of light separately along different axes.

FIG. 19B is a top side sectional elevational view of the set ofcollimation lenses of FIG. 19A.

FIGS. 19C and 19D are isometric views of exemplary lens shapes whichcould be used as lenses in the implementation of FIGS. 19A and 19B.

FIG. 20A is a left side sectional view of a set of collimation lensesfor circularizing and collimating a beam of light.

FIG. 20B is a top side sectional elevational view of the set ofcollimation lenses of FIG. 20A.

FIGS. 20C and 20D are isometric views of exemplary lens shapes whichcould be used as a collimation lens in the implementation of FIGS. 20Aand 20B.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedimplementations. However, one skilled in the relevant art will recognizethat implementations may be practiced without one or more of thesespecific details, or with other methods, components, materials, etc. Inother instances, well-known structures associated with computer systems,server computers, and/or communications networks have not been shown ordescribed in detail to avoid unnecessarily obscuring descriptions of theimplementations.

Unless the context requires otherwise, throughout the specification andclaims that follow, the word “comprising” is synonymous with“including,” and is inclusive or open-ended (i.e., does not excludeadditional, unrecited elements or method acts).

Reference throughout this specification to “one implementation” or “animplementation” means that a particular feature, structure orcharacteristic described in connection with the implementation isincluded in at least one implementation. Thus, the appearances of thephrases “in one implementation” or “in an implementation” in variousplaces throughout this specification are not necessarily all referringto the same implementation. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more implementations.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contextclearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theimplementations.

One or more implementations of the present disclosure providelaser-based optical engines, for example, laser-based optical enginesfor laser projectors used in wearable heads-up displays or otherapplications. Generally, the optical engines discussed herein integratea plurality of laser dies or diodes (e.g., 3 laser diodes, 4 laserdiodes) within a single, hermetically or partially hermetically sealed,encapsulated package. As discussed further below with reference to FIGS.6-9, in at least some implementations, photonic integrated circuitshaving input facets (e.g., edge couplers, grating couplers) may be usedto wavelength multiplex beams of light emitted by the plurality of laserdiodes into a coaxially superimposed aggregate beam. Alternatively, eachwavelength of light may be channeled individually through the photonicintegrated circuit. As discussed below with reference to FIGS. 14-15, inat least some implementations, the laser diodes are coupled to thephotonic integrated circuit via directly written waveguides. In at leastsome implementations, the waveguide medium in which the waveguides arewritten may also provide a seal for the laser diodes, therebyeliminating the need for a separate cap to hermetically or partiallyhermetically seal the laser diodes on a base substrate, for example.

As discussed below with reference to FIGS. 17A-17B, in at least someimplementations, an optical engine may include a grating waveguidecombiner that inputs light emitted from the plurality of laser diodesand outputs a superimposed collimated beam, as discussed further belowwith reference to FIGS. 17A and 17B. Such optical engines may havevarious advantages over existing designs including, for example, smallervolume, lower weight, better manufacturability, lower cost, fastermodulation speed, etc. The material used for the optical enginesdiscussed herein may be any suitable materials, e.g., ceramics withadvantageous thermal properties, etc. As noted above, such features areparticularly advantages in various applications including WHUDs.

FIG. 1A is a left side, elevational sectional view of an optical engine100, which may also be referred to as a “multi-laser diode module” or an“RGB laser module,” in accordance with the present systems, devices, andmethods. FIG. 1B is a front side, elevational sectional view of theoptical engine 100. The optical engine 100 includes a base substrate 102having a top surface 104 and a bottom surface 106 opposite the topsurface. The base substrate 102 may be formed from a material that isradio frequency (RF) compatible and is suitable for hermetic sealing.For example, the base substrate 102 may be formed from low temperatureco-fired ceramic (LTCC), aluminum nitride (AlN), alumina, aluminumnitride (AlN), Kovar®, other ceramics with suitable thermal properties,etc. The term Kovar® generally refers to iron-nickel-cobalt alloyshaving similar thermal expansion coefficients to glass and ceramics,thus making Kovar® materials particularly suitable for forming hermeticseals which remain functional in a wide range of temperatures.

The optical engine 100 also includes a plurality of chip submounts 108a-108 d (collectively 108) bonded (e.g., attached) to the top surface104 of the base substrate 102. The plurality of chip submounts 108 arealigned in a row across a width of the optical engine 100 between theleft and right sides thereof. Each of the plurality of chip submounts108 includes a laser diode 110, also referred to as a laser chip orlaser die, bonded thereto. In particular, an infrared chip submount 108a carries an infrared laser diode 110 a, a red chip submount 108 bcarries a red laser diode 110 b, a green chip submount 108 c carries agreen laser diode 110 c, and a blue chip submount 108 d carries a bluelaser diode 110 d. In operation, the infrared laser diode 110 a providesinfrared laser light, the red laser diode 110 b provides red laserlight, the green laser diode 110 c provides green laser light, and theblue laser diode 110 d provides blue laser light. Each of the laserdiodes 110 may comprise one of an edge emitter laser or avertical-cavity surface-emitting laser (VCSEL), for example. Each of thefour laser diode/chip submount pairs may be referred to collectively asa “laser chip on submount,” or a laser CoS 112. Thus, the optical engine100 includes an infrared laser CoS 112 a, a red laser CoS 112 b, a greenlaser CoS 112 c, and a blue laser CoS 112 d. In at least someimplementations, one or more of the laser diodes 110 may be bondeddirectly to the base substrate 102 without use of a submount 108. Itshould be appreciated that although some implementations discussedherein describe laser diodes as chips or dies on submounts, other diesor types of devices, e.g., p-side down devices, may be used as well.

The optical engine 100 also includes a laser diode driver circuit 114bonded to the bottom surface 106 of the base substrate 102. The laserdiode driver circuit 114 is operatively coupled to the plurality oflaser diodes 110 via suitable electrical connections 116 to selectivelydrive current to the plurality of laser diodes. In at least someimplementations, the laser diode driver circuit 114 may be positionedrelative to the CoSs 112 to minimize the distance between the laserdiode driver circuit 114 and the CoSs 112. Although not shown in FIGS.1A and 1B, the laser diode driver circuit 114 may be operativelycoupleable to a controller (e.g., microcontroller, microprocessor, ASIC)which controls the operation of the laser diode driver circuit 114 toselectively modulate laser light emitted by the laser diodes 110. In atleast some implementations, the laser diode driver circuit 114 may bebonded to another portion of the base substrate 102, such as the topsurface 104 of the base substrate. In at least some implementations, thelaser diode driver circuitry 114 may be remotely located and operativelycoupled to the laser diodes 110. In order to not require the use ofimpedance matched transmission lines, the size scale may be smallcompared to a wavelength (e.g., lumped element regime), where theelectrical characteristics are described by (lumped) elements likeresistance, inductance, and capacitance.

Proximate the laser diodes 110 there is positioned an optical directorelement 118. Like the chip submounts 108, the optical director element118 is bonded to the top surface 104 of the base substrate 102. In theillustrated example, the optical director element 118 has a triangularprism shape that includes a plurality of planar faces. In particular theoptical director element 118 includes an angled front face 118 a thatextends along the width of the optical engine 100, a rear face 118 b, abottom face 118 c that is bonded to the top surface 104 of the basesubstrate 102, a left face 118 d, and a right face 118e opposite theleft face. The optical director element 118 may comprise a mirror or aprism, for example.

The optical engine 100 also includes a cap 120 that includes a verticalsidewall 122 having a lower first end 124 and an upper second end 126opposite the first end. A flange 128 may be disposed around a perimeterof the sidewall 122 adjacent the lower first end 124. Proximate theupper second end 126 of the sidewall 122 there is a horizontal opticalwindow 130 that forms the “top” of the cap 120. The sidewall 122 and theoptical window 130 together define an interior volume 132 sized anddimensioned to receive the plurality of chip submounts 108, theplurality of laser diodes 110, and the optical director element 118. Thelower first end 124 and the flange 128 of the cap 120 are bonded to thebase substrate 102 to provide a hermetic or partially hermetic sealbetween the interior volume 132 of the cap and a volume 134 exterior tothe cap.

As shown best in FIG. 1A, the optical director element 118 is positionedand oriented to direct (e.g., reflect) laser light received from each ofthe plurality of laser diodes 110 upward (as shown) toward the opticalwindow 130 of the cap 120, wherein the laser light exits the interiorvolume 132.

The cap 120 may have a round shape, rectangular shape, or other shape.Thus, the vertical sidewall 122 may comprise a continuously curvedsidewall, a plurality (e.g., four) of adjacent planar portions, etc. Theoptical window 130 may comprise an entire top of the cap 120, or maycomprise only a portion thereof. In at least some implementations, theoptical window 130 may be located on the sidewall 122 rather thanpositioned as a top of the cap 120, and the laser diodes 110 and/or theoptical director element 118 may be positioned and oriented to directthe laser light from the laser diodes toward the optical window on thesidewall 122. At least some implementations may not include opticaldirector element 118 such that laser light from the laser diodes may beoutput towards the optical window on the sidewall 122 without the needfor intervening optical elements. In at least some implementations, thecap 120 may include a plurality of optical windows instead of a singleoptical window.

The optical engine 100 also includes four collimation/pointing lenses136 a-136 d (collectively 136), one for each of the four laser diodes110 a-110 d, respectively, that are bonded to a top surface 138 of theoptical window 130. Each of the plurality of collimation lenses 136 ispositioned and oriented to receive light from a corresponding one of thelaser diodes 110 through the optical window 130. In particular, thecollimation lens 136 a receives light from the infrared laser diode 110a via the optical director element 118 and the optical window 130, thecollimation lens 136 b receives light from the red laser diode 110 b viathe optical director element and the optical window, the collimationlens 136 c receives light from the green laser diode 110 c via theoptical director element and the optical window, and the collimationlens 136 d receives light from the blue laser diode 110 d via theoptical director element and the optical window.

Each of the collimation lenses 136 is operative to receive laser lightfrom a respective one of the laser diodes 110, and to generate a singlecolor beam. In particular, the collimation lens 136 a receives infraredlaser light from the infrared laser diode 110 a and produces an infraredlaser beam 138 a, the collimation lens 136 b receives red laser lightfrom the red laser diode 110 b and produces a red laser beam 138 b, thecollimation lens 136 c receives green laser light from the green laserdiode 110 c and produces a green laser beam 138 c, and the collimationlens 136 d receives blue laser light from the blue laser diode 110 d andproduces a blue laser beam 138 d.

The optical engine 100 may also include, or may be positioned proximateto, a beam combiner 140 that is positioned and oriented to combine thelight beams 138 a-138 d received from each of the collimation lenses 136into a single aggregate beam 142. As an example, the beam combiner 140may include one or more diffractive optical elements (DOE) and/orrefractive/reflective optical elements that combine the different colorbeams 138 a-138 d in order to achieve coaxial superposition. An examplebeam combiner is shown in FIG. 3 and discussed below.

In at least some implementations, the laser CoSs 112, the opticaldirector element 118, and/or the collimation lenses 136 may bepositioned differently. As noted above, laser diode driver circuit 114may be mounted on the top surface 104 or the bottom surface 106 of thebase substrate 102, depending on the RF design and other constraints(e.g., package size). In at least some implementations, the opticalengine 100 may not include the optical director element 118, and thelaser light may be directed from the laser diodes 110 toward thecollimation lenses 136 without requiring an intermediate opticaldirector element. Additionally, in at least some implementations, one ormore of the laser diodes may be mounted directly on the base substrate102 without use of a submount.

For the sake of a controlled atmosphere inside the interior volume 132,it may be desirable to have no organic compounds inside the interiorvolume 132. In at least some implementations, the components of theoptical engine 100 may be bonded together using no adhesives. In otherimplementations, a low amount of adhesives may be used to bond at leastone of the components, which may reduce cost while providing arelatively low risk of organic contamination for a determined lifetime(e.g., 2 or more years) of the optical engine 100. The use of adhesivesmay result in a partial hermetic seal, but this partial hermetic sealmay be acceptable in certain applications, as detailed below.

Generally, “hermetic” refers to a seal which is airtight, that is, aseal which excludes the passage of air, oxygen, and other gases.“Hermetic” within the present specification carries this meaning.Further, “partially hermetic” as used herein refers to a seal whichlimits, but does not necessarily completely prevent, the passage ofgases such as air. “Partially hermetic” as used herein may alternativelybe stated as “reduced hermiticity”. In the example above, adhesives maybe used to bond components. Such adhesives may result in a seal beingnot completely hermetic, in that some amount of gasses may slowly leakthrough the adhesive. However, such a seal can still be considered“partially hermetic” or as having “reduced hermiticity”, because theseal reduces the flow of gasses therethrough.

In one example application, even in an environment with only partialhermiticity, the life of laser diodes 110 and transparency of opticalwindow 130 may be maintained longer than the life of a battery of adevice, such that partial hermiticity may be acceptable for the devices.In some cases, even protecting interior volume 132 from particulate witha dust cover may be sufficient to maintain laser diodes 110 andtransparency of optical window 130 for the intended lifespan of thedevice. In some cases, laser diodes 110 and transparency of opticalwindow 130 may last for the intended lifespan of the device even withouta protective cover. Various bonding processes (e.g., attachingprocesses) for the optical engine 100 are discussed below with referenceto FIG. 5.

FIG. 2 is a flow diagram of a method 200 of operating an optical engine,in accordance with the present systems, devices, and methods. The method200 may be implemented using the optical engine 100 of FIGS. 1A-1B, forexample. It should be appreciated that methods of operating opticalengines according to the present disclosure may include fewer oradditional acts than set forth in the method 200. Further, the actsdiscussed below may be performed in an order different than the orderpresented herein.

At 202, at least one controller may cause a plurality of laser diodes ofan optical engine to generate laser light. As discussed above, theplurality of laser diodes may be hermetically or partially hermeticallysealed in an encapsulated package. The laser diodes may produce lightsequentially and/or simultaneously with each other. At 204, at least oneoptical director element may optionally receive the laser light from thelaser diodes. The optical director element may comprise a mirror or aprism, for example. As discussed above, in at least some implementationsthe optical engine may be designed such that laser light exits theoptical engine without use of an optical director element.

At 206, the at least one optical director element, if included, maydirect the received laser light toward an optical window of theencapsulated package. For example, the optical director element mayreflect the received laser light toward the optical window of theencapsulated package. In implementations without at least one opticaldirector element, the laser light generated by the plurality of laserdiodes may be output directly toward the optical window of theencapsulated package.

At 208, a plurality of collimation lenses may collimate the laser lightfrom the laser diodes that exits the encapsulated package via theoptical window to generate a plurality of differently colored laserlight beams. The collimation lenses may be positioned inside or outsideof the encapsulated package. As an example, the collimation lenses maybe physically coupled to the optical window of the encapsulated package.

At 210, a beam combiner may combine the plurality of laser light beamsreceived from each of the collimation lenses into a single aggregatebeam. The beam combiner may include one or more diffractive opticalelements (DOE) that combine different color beams in order to achievecoaxial superposition, for example. The beam combiner may include one ormore DOEs and/or one or more refractive/reflective optical elements. Anexample beam combiner is shown in FIG. 3 and discussed below.

FIG. 3 is a schematic diagram of a wearable heads-up display (WHUD) 300with an exemplary laser projector 302, and a transparent combiner 304 ina field of view of an eye 306 of a user of the WHUD, in accordance withthe present systems, devices, and methods. The WHUD 300 includes asupport structure (not shown), with the general shape and appearance ofan eyeglasses frame, carrying an eyeglass lens 308 with the transparentcombiner 304, and the laser projector 302.

The laser projector 302 comprises a controller or processor 310, anoptical engine 312 comprising four laser diodes 314 a, 314 b, 314 c, 314d (collectively 314) communicatively coupled to the processor 310, abeam combiner 316, and a scan mirror 318. The optical engine 312 may besimilar or identical to the optical engine 100 discussed above withreference to FIGS. 1A and 1B. Generally, the term “processor” refers tohardware circuitry, and may include any of microprocessors,microcontrollers, application specific integrated circuits (ASICs),digital signal processors (DSPs), programmable gate arrays (PGAs),and/or programmable logic controllers (PLCs), or any other integrated ornon-integrated circuit.

During operation of the WHUD 300, the processor 310 modulates lightoutput from the laser diodes 314, which includes a first red laser diode314 a (R), a second green laser diode 314 b (G), a third blue laserdiode 314 c (B), and a fourth infrared laser diode 314 d (IR). The firstlaser diode 314 a emits a first (e.g., red) light signal 320, the secondlaser diode 314 b emits a second (e.g., green) light signal 322, thethird laser diode 314 c emits a third (e.g., blue) light signal 324, andthe fourth laser diode 314 d emits a fourth (e.g., infrared) lightsignal 326. All four of light signals 320, 322, 324, and 326 enter orimpinge on the beam combiner 316. Beam combiner 316 could for example bebased on any of the beam combiners described in U.S. Provisional PatentApplication Ser. No. 62/438,725, U.S. Non-Provisional patent applicationSer. No. 15/848,265 (U.S. Publication Number 2018/0180885), U.S.Non-Provisional patent application Ser. No. 15/848,388 (U.S. PublicationNumber 2018/0180886), U.S. Provisional Patent Application Ser. No.62/450,218, U.S. Non-Provisional patent application Ser. No. 15/852,188(U.S. Publication Number 2018/0210215), U.S. Non-Provisional patentapplication Ser. No. 15/852,282, (U.S. Publication Number 2018/0210213),and/or U.S. Non-Provisional patent application Ser. No. 15/852,205 (U.S.Publication Number 2018/0210216).

In the illustrated example, the beam combiner 316 includes opticalelements 328, 330, 332, and 334. The first light signal 320 is emittedtowards the first optical element 328 and reflected by the first opticalelement 328 of the beam combiner 316 towards the second optical element330 of the beam combiner 316. The second light signal 322 is alsodirected towards the second optical element 330. The second opticalelement 330 is formed of a dichroic material that is transmissive of thered wavelength of the first light signal 320 and reflective of the greenwavelength of the second light signal 322. Therefore, the second opticalelement 330 transmits the first light signal 320 and reflects the secondlight signal 322. The second optical element 330 combines the firstlight signal 320 and the second light signal 322 into a single aggregatebeam (shown as separate beams for illustrative purposes) and routes theaggregate beam towards the third optical element 332 of the beamcombiner 316.

The third light signal 324 is also routed towards the third opticalelement 332. The third optical element 332 is formed of a dichroicmaterial that is transmissive of the wavelengths of light (e.g., red andgreen) in the aggregate beam comprising the first light signal 320 andthe second light signal 322 and reflective of the blue wavelength of thethird light signal 324. Accordingly, the third optical element 332transmits the aggregate beam comprising the first light signal 320 andthe second light signal 322 and reflects the third light signal 324. Inthis way, the third optical element 332 adds the third light signal 324to the aggregate beam such that the aggregate beam comprises the lightsignals 320, 322, and 324 (shown as separate beams for illustrativepurposes) and routes the aggregate beam towards the fourth opticalelement 334 in the beam combiner 316.

The fourth light signal 326 is also routed towards the fourth opticalelement 334. The fourth optical element 334 is formed of a dichroicmaterial that is transmissive of the visible wavelengths of light (e.g.,red, green, and blue) in the aggregate beam comprising the first lightsignal 320, the second light signal 322, and the third light signal 324and reflective of the infrared wavelength of the fourth light signal326. Accordingly, the fourth optical element 334 transmits the aggregatebeam comprising the first light signal 320, the second light signal 322,and the third light signal 324 and reflects the fourth light signal 326.In this way, the fourth optical element 334 adds the fourth light signal326 to the aggregate beam such that the aggregate beam 336 comprisesportions of the light signals 320, 322, 324, and 326. The fourth opticalelement 334 routes the aggregate beam 336 towards the controllable scanmirror 318.

The scan mirror 318 is controllably orientable and scans (e.g. rasterscans) the beam 336 to the eye 306 of the user of the WHUD 300. Inparticular, the controllable scan mirror 318 scans the laser light ontothe transparent combiner 304 carried by the eyeglass lens 308. The scanmirror 318 may be a single bi-axial scan mirror or two single-axis scanmirrors may be used to scan the laser light onto the transparentcombiner 304, for example. In at least some implementations, thetransparent combiner 304 may be a holographic combiner with at least oneholographic optical element. The transparent combiner 304 redirects thelaser light towards a field of view of the eye 306 of the user. Thelaser light redirected towards the eye 306 of the user may be collimatedby the transparent combiner 304, wherein the spot at the transparentcombiner 304 is approximately the same size and shape as the spot at theeye 306 of the user. The laser light may be converged by the eye 306 toa focal point at the retina of eye 306 and creates an image that isfocused. The visible light may create display content in the field ofview of the user, and the infrared light may illuminate the eye 306 ofthe user for the purpose of eye tracking.

FIG. 4 is a schematic diagram of a wearable heads-up display (WHUD) 400with a laser projector 402 in accordance with the present systems,devices, and methods. WHUD 400 includes a support structure 404 with theshape and appearance of a pair of eyeglasses that in use is worn on thehead of the user. The support structure 404 carries multiple components,including eyeglass lens 406, a transparent combiner 408, the laserprojector 402, and a controller or processor 410. The laser projector402 may be similar or identical to the laser projector 302 of FIG. 3.For example, the laser projector 402 may include an optical engine, suchas the optical engine 100 or the optical engine 312. The laser projector402 may be communicatively coupled to the controller 410 (e.g.,microprocessor) which controls the operation of the projector 402, asdiscussed above. The controller 410 may include or may becommunicatively coupled to a non-transitory processor-readable storagemedium (e.g., memory circuits such as ROM, RAM, FLASH, EEPROM, memoryregisters, magnetic disks, optical disks, other storage), and thecontroller may execute data and/or instruction from the non-transitoryprocessor readable storage medium to control the operation of the laserprojector 402.

In operation of the WHUD 400, the controller 410 controls the laserprojector 402 to emit laser light. As discussed above with reference toFIG. 3, the laser projector 402 generates and directs an aggregate beam(e.g., aggregate beam 336 of FIG. 3) toward the transparent combiner 408via at least one controllable mirror (not shown in FIG. 4). Theaggregate beam is directed towards a field of view of an eye of a userby the transparent combiner 408. The transparent combiner 408 maycollimate the aggregate beam such that the spot of the laser lightincident on the eye of the user is at least approximately the same sizeand shape as the spot at transparent combiner 408. The transparentcombiner 408 may be a holographic combiner that includes at least oneholographic optical element.

FIG. 5 is a flow diagram of a method 500 of manufacturing an opticalengine, in accordance with the present systems, devices, and methods.The method 500 may be implemented to manufacture the optical engine 100of FIGS. 1A-1B or the optical engine 312 of FIG. 3, for example. Itshould be appreciated that methods of manufacturing optical enginesaccording to the present disclosure may include fewer or additional actsthan set forth in the method 500. Further, the acts discussed below maybe performed in an order different than the order presented herein.

At 502, a plurality of laser diodes may be bonded to a respectiveplurality of submounts. In at least some implementations, this methodmay be performed by an entity different than that manufacturing theoptical engine. For example, in at least some implementations, one ormore of the plurality of laser diodes (e.g., green laser diode, bluelaser diode) may be purchased as already assembled laser CoSs. For easeof handling and simplification of the overall process, in at least someimplementations it may be advantageous to also bond laser diodes thatcannot be procured on submounts to a submount as well. As a non-limitingexample, in at least some implementations, one or more of the laserdiodes may be bonded to a corresponding submount using an eutectic goldtin (AuSn) solder process, which is flux-free and requires heating uptop 280° C.

At 504, the plurality of CoSs may be bonded to a base substrate.Alternatively, act 502 could be skipped for at least one or all of thelaser diodes, and act 504 could comprise bonding the at least one or allof the laser diodes directly to the base substrate. The base substratemay be formed from a material that is RF compatible and is suitable forhermetic sealing. For example, the base substrate may be formed from lowtemperature co-fired ceramic (LTCC), aluminum nitride (AlN), alumina,aluminum nitride (AlN), Kovar®, etc. Since several CoSs are bonded nextto each other on the same base substrate, it may be advantageous toeither “step-solder” them sequentially or to use a bonding techniquethat does not rely on re-melting of solder materials. Forstep-soldering, each subsequent soldering step utilizes a processtemperature that is less than the process temperatures of previoussolder steps to prevent re-melting of solder materials. It may also beimportant that the laser diode-to-submount bonding does not re-meltduring bonding of the CoSs to the base substrate. Bonding technologiesother than step-soldering that may be used include parallel soldering ofall CoS in reflow oven process, thermosonic or thermocompressionbonding, transient liquid phase (TLP) bonding, laser soldering, etc.Some of these example bonding technologies are discussed below.

For parallel soldering of all CoSs in a reflow oven process, appropriatetooling is required to assure proper bonding and alignment during theprocess. An advantage of this process is the parallel and hence timeefficient bonding of all CoSs at once and even many assemblies inparallel. A possible disadvantage of this process is the potential lossof the alignment of components during the reflow process. Generally, asoldering cycle ideally needs a few minutes of dwell time. Preheatingmay be used to reduce the soldering time, which requires a few minutesfor such a process depending on the thermal mass of the components beingbonded. Thus, a batch process may be used with regular soldering toreduce the assembly costs with high throughput at the expense ofalignment tolerance.

For thermosonic or thermocompression bonding, thick gold metallizationmay be used but no extra solder layer is required. The temperatures forthermocompression bonding might be as high as 300 to 350° C. to have agood bond with a good thermal conductivity. Thermosonic bonding may beused to reduce the pressure and temperature needed for bonding, whichmay be required for at least some components that might not tolerate thetemperatures required for thermocompression bonding.

Transient liquid phase (TLP) bonding may also be used. There are manydifferent reaction couples that may be used, including gold-tin,copper-tin, etc. With this method, a liquid phase is formed during thebonding which will solidify at the same temperature. The re-meltingtemperatures of the bond are much higher than the solderingtemperatures.

In at least some implementations, laser soldering may be used to bondsome or all of the components of the optical engine. Generally, thethermal characteristic of the parts to be bonded may be important whenimplementing a laser soldering process.

Subsequent reflows of solder are not recommended due to liquid phasereaction or dissolution mechanisms which may reduce the reliability ofthe joint. This could result in voiding at the interface or a reductionin strength of the joint itself. In order to mitigate potential reflowdissolution problems, other options can be taken into consideration,which do not rely on extreme heating of the device and can be favorablein terms of production cost. For example, bonding of the base substratewith adhesives (electrically conductive for common mass, ornon-conductive for floating) may be acceptable with respect to heattransfer and out-gassing as discussed regarding partial hermetic sealingabove.

Further, in at least some implementations, a reactive multi-layer foilmaterial (e.g., NanoFoil®) or a similar material may be used as a solderpre-form, which enables localized heat transfer. A reactive multi-layerfoil material is a metallic material based on a plurality (e.g.,hundreds, thousands) of reactive foils (aluminum and nickel) thatenables die-attach soldering (e.g., silicon chip onto stainless steelpart). In such implementations, dedicated heat transfer supportmetallizations may be deposited onto the two components being joinedtogether. This method may be more advantageous for CoS-to-base substratemounting compared to chip-to-submount bonding. Generally, bonding usingreactive multi-layer foil materials enables furnace-free,low-temperature soldering of transparent or non-transparent components,without reaching the bonding temperatures for solder reflow processes.Reactive multi-layer foil materials can be patterned with a ps-laserinto exact preform shapes.

At 506, the optical director element, if included, may be bonded to thebase substrate proximate the laser CoSs. The optical director elementmay be bonded to the base substrate using any suitable bonding process,including the bonding processes discussed above with reference to act504.

At 508, the laser diode driver circuit may optionally be bonded to thebase substrate. As noted above, the laser diode driver circuit may bebonded to the base substrate such that the distance between the laserdiode driver circuit and the laser CoSs is minimized. This may alsocomprise positioning a plurality of electrical connections whichoperatively couple the laser diode driver circuit to the plurality oflaser diodes as shown in FIGS. 16A and 16B. In alternativeimplementations, the laser diode driver circuit may be bonded to aseparate base substrate from the other components mentioned above asshown in FIG. 16B. The process used to bond the laser diode drivercircuit to the base substrate may be any suitable bonding process, suchas bonding processes commonly used to bond surface mount devices (SMD)to circuit boards. In other alternative implementations, the laser diodedriver circuit may be mounted directly to a frame of a WHUD. Forimplementations where the laser diode drive circuit is not bonded to thesame base substrate as the other components mentioned above, a pluralityof electrical contacts and electrical connections could be bonded to thebase substrate, each electrical connection operatively connecting arespective electrical contact to a respective laser diode. Subsequently,the at least one laser driver circuit could be operatively coupled tothe electrical contacts, which will then electrically couple the laserdiode drive circuit to the electrical connections and consequently tothe laser diodes. Exemplary arrangements of electrical connections andelectrical contacts is discussed later with reference to FIG. 16B.

At 510, the cap may optionally be bonded to the base substrate to form ahermetic or partially hermetic seal as discussed above between theinterior volume of the encapsulated package and an exterior environment.As noted above, it may be desirable to maintain a specific atmospherefor the laser diode chips for reliability reasons. In at least someimplementations, adhesive sealing may be undesirable because of the highpermeability of gases. This is especially the case for blue laserdiodes, which emit blue laser light that may bake contamination onfacets and windows, thereby reducing transparency of the optical window.However, as detailed above regarding FIGS. 1A and 1B, partialhermiticity, a particulate dust cover, or even no protective cover maybe acceptable for certain applications. In implementations where the capwould be bonded over electrical connections which connect the at leastone laser diode driver circuit to the plurality of laser diodes, such aswhen the at least one laser diode driver circuit is bonded to the sameside of a base substrate as the laser diodes, or when the at least onelaser diode driver circuit is coupled to electrical contacts bonded tothe same side of the base substrate as the laser diodes, an electricallyinsulating cover can first be bonded to the base substrate over theelectrical connections. Subsequently, the cap can be bonded at leastpartially to the electrically insulating cover, and potentially to aportion of the base substrate if the insulating cover does not fullyencircle the intended interior volume. In this way, at least a portionof the cap will be bonded to the base substrate indirectly by beingbonded to the electrically insulating cover. In some implementations,the entire cap could be bonded to the base substrate indirectly by beingbonded to an electrically insulating cover which encircles the intendedinterior volume. Exemplary electrically insulating covers are discussedlater with reference to FIGS. 16A and 16B.

During the sealing process, the atmosphere may be defined by floodingthe package accordingly. For example, the interior volume of theencapsulated package may be flooded with an oxygen enriched atmospherethat burns off contaminants which tend to form on interfaces where thelaser beam is present. The sealing itself may also be performed so as toprevent the exchange between the package atmosphere and the environment.Due to limitations concerning the allowed sealing temperature, e.g., thecomponents inside the package should not be influenced, in at least someimplementations seam welding or laser assisted soldering/diffusionbonding may be used. In at least some implementations, localized sealingusing a combination of seam welding and laser soldering may be used.

At 512, the collimation lenses may be actively aligned. For example,once the laser diode driver circuit has been bonded and the cap has beensealed, the laser diodes can be turned on and the collimations lensesfor each laser diode can be actively aligned. In at least someimplementations, each of the collimation lenses may be positioned tooptimize spot as well as pointing for each of the respective laserdiodes.

At 514, the beam combiner may be positioned to receive and combineindividual laser beams into an aggregate beam. As discussed above, thebeam combiner may include one or more diffractive optical elementsand/or one or more refractive/reflective optical elements that functionto combine the different color beams into an aggregate beam. Theaggregate beam may be provided to other components or modules, such as ascan mirror of a laser projector, etc.

FIG. 6 is a top plan view of a photonic integrated circuit 600 forwavelength multiplexing followed by a common collimation lens 602 and anoptional diffractive optical element 604. The photonic integratedcircuit 600 may be a component in an optical engine, such as an opticalengine 700 of FIG. 7, an optical engine as shown in FIG. 12A, or anoptical engine as shown in FIG. 12B discussed further below. Thephotonic integrated circuit 600 includes a plurality of input facets 612a-612 d and at least one output facet 608 (e.g., output optical coupleror grating output coupler). In FIG. 6, input facets 612 a-612 d areshown as grating couplers (also referred to as “diffractive gratingcouplers” or “grating input couplers”) on a top surface 606 thereof, butother input facets are possible such as illustrated in FIG. 12Bdiscussed below. In operation, the photonic integrated circuit 600receives a plurality of beams of light 610 a-610 d that are coupled tothe photonic integrated circuit via the input facets 612 a-612 d,respectively, and wavelength multiplexes the plurality of beams toprovide a coaxially superimposed aggregate beam of light 614 that exitsthe photonic integrated circuit at the output facet 608, such as anoutput optical coupler or grating output coupler. Compared to edgecoupling, in at least some applications using grating input couplers forinput facets 612 a-612 d may allow for relaxed tolerances for beamalignment. Generally, the photonic integrated circuit 600 may includeone or more diffractive optical elements (DOE) and/orrefractive/reflective optical elements that combine the different colorbeams 610 a-610 d in order to achieve coaxial superposition.

Following out-coupling of the aggregate beam 614 from the output facet608 of the photonic integrated circuit 600, the aggregated beam iscollimated via the common collimation lens 602. In at least someimplementations, the collimation lens 602 may be either an achromaticlens or an apochromatic lens (or lens assemblies), depending on theparticular optical design and tolerances of the system. In at least someimplementations, one or more diffractive optical elements 604 may beused to provide wavelength dependent focus correction.

FIG. 7 is a left side sectional elevational view of the optical engine700. The optical engine 700 includes several components that may besimilar or identical to the components of the optical engine 100 ofFIGS. 1A and 1B. Thus, some or all of the discussion above may beapplicable to the optical engine 700.

The optical engine 700 includes a base substrate 702 having a topsurface 704 and a bottom surface 706 opposite the top surface. The basesubstrate 702 may be formed from a material that is radio frequency (RF)compatible and is suitable for hermetic sealing. For example, the basesubstrate 702 may be formed from low temperature co-fired ceramic(LTCC), aluminum nitride (AlN), alumina, aluminum nitride (AlN), Kovar®,etc.

The optical engine 700 also includes a plurality of chip submounts 708(only one chip submount visible in the sectional view of FIG. 7) thatare bonded (e.g., attached) to the top surface 704 of the base substrate702. The plurality of chip submounts 708 are aligned in a row across awidth of the optical engine 700 between the left and right sidesthereof. Each of the plurality of chip submounts 708 includes a laserdiode 710, also referred to as a laser chip or laser die, bondedthereto. In particular, an infrared chip submount carries an infraredlaser diode, a red chip submount carries a red laser diode, a green chipsubmount carries a green laser diode, and a blue chip submount carries ablue laser diode. In operation, the infrared laser diode providesinfrared laser light, the red laser diode provides red laser light, thegreen laser diode provides green laser light, and the blue laser diodeprovides blue laser light. Each of the laser diodes 710 may comprise oneof an edge emitter laser or a vertical-cavity surface-emitting laser(VCSEL), for example. Each of the four laser diode/chip submount pairsmay be referred to collectively as a “laser chip on submount,” or alaser CoS 712. Thus, the optical engine 700 includes an infrared laserCoS, a red laser CoS, a green laser CoS, and a blue laser CoS. In atleast some implementations, one or more of the laser diodes 710 may bebonded directly to the base substrate 702 without use of a submount 708.

The optical engine 700 also includes a laser diode driver circuit 714bonded to the bottom surface 706 of the base substrate 702. The laserdiode driver circuit 714 is operatively coupled to the plurality oflaser diodes 710 via suitable electrical connections 716 to selectivelydrive current to the plurality of laser diodes. Generally, the laserdiode driver circuit 714 may be positioned relative to the CoSs 712 tominimize the distance between the laser diode driver circuit 714 and theCoSs 712. Although not shown in FIG. 7, the laser diode driver circuit714 may be operatively coupleable to a controller (e.g.,microcontroller, microprocessor, ASIC) that controls the operation ofthe laser diode driver circuit 714 to selectively modulate laser lightemitted by the laser diodes 710. In at least some implementations, thelaser diode driver circuit 714 may be bonded to another portion of thebase substrate 702, such as the top surface 704 of the base substrate,similar to the implementations shown in FIG. 16A. In at least someimplementations, the laser diode driver circuitry 714 may be remotelylocated and operatively coupled to the laser diodes 710. In order to notrequire the use of impedance matched transmission lines, the size scalemay be small compared to a wavelength (e.g., lumped element regime),where the electrical characteristics are described by (lumped) elementslike resistance, inductance, and capacitance.

Proximate the laser diodes 710 there is positioned an optical directorelement 718. Like the chip submounts 708, the optical director element718 is bonded to the top surface 704 of the base substrate 702. In theillustrated example, the optical director element 718 has a triangularprism shape that includes a plurality of planar faces. In particular theoptical director element 718 includes an angled front face 718 a thatextends along the width of the optical engine 700, a rear face 718 b, abottom face 718 c that is bonded to the top surface 704 of the basesubstrate 702, a left face 718 d, and a right face 718e opposite theleft face. The optical director element 718 may comprise a mirror or aprism, for example. In at least some implementations, the angled frontface 718 a may be curved to provide fast axis collimation of the laserlight from the laser diodes 710.

The optical engine 700 also includes a cap 720 that includes a verticalsidewall 722 having a lower first end 724 and an upper second end 726opposite the first end. A flange 728 may be disposed around a perimeterof the sidewall 722 adjacent the lower first end 724. Proximate theupper second end 726 there of the sidewall 722 there is a horizontal (asshown) optical window 730 that forms the “top” of the cap 120. Thesidewall 722 and the optical window 730, along with a portion of the topsurface 704 of the base substrate 702, together define an interiorvolume 732 sized and dimensioned to receive the plurality of chipsubmounts 708, the plurality of laser diodes 710, and the opticaldirector element 717. The lower first end 724 and the flange 728 of thecap 720 are bonded to the base substrate 702 to provide a hermetic orpartially hermetic seal between the interior volume 732 of the cap and avolume 734 exterior to the cap.

The optical director element 718 is positioned and oriented to direct(e.g., reflect) laser light received from each of the plurality of laserdiodes 710 upward (as shown) toward the optical window 730 of the cap720, wherein the laser light exits the interior volume 732.

The cap 720 may have a round shape, rectangular shape, or other shape.Thus, the vertical sidewall 722 may comprise a continuously curvedsidewall, a plurality (e.g., four) of adjacent planar portions, etc. Theoptical window 730 may comprise an entire top of the cap 720, or maycomprise only a portion thereof In at least some implementations, theoptical window 730 may be located on the sidewall 722 rather thanpositioned as a top of the cap 720, and the laser diodes 710 and/or theoptical director element 718 (if present) may be positioned and orientedto direct the laser light from the laser diodes toward the opticalwindow on the sidewall 722. In at least some implementations, the cap720 may include a plurality of optical windows instead of a singleoptical window 730.

In at least some implementations, the optical engine 700 optionallyincludes four collimation lenses 736 (only one visible in the sectionalview of FIG. 7), one for each of the four laser diodes 710. In otherimplementations, the collimation lenses 736 are omitted. In theillustrated implementation, the collimation lenses 736 are bonded to abottom surface of the optical window 730 in a row, although thecollimation lenses may be positioned differently in otherimplementations. For example, in at least some implementations, thecollimation lenses 736 may be positioned outside of the package (e.g.,outside of the interior volume 732) rather than inside the package asshown in FIG. 7. Each of the plurality of collimation lenses 736 may bepositioned and oriented to receive light from a corresponding one of thelaser diodes 710, and to direct collimated light upward (as shown)through the optical window 730 toward the photonic integrated circuit600, which is shown “inverted” in FIG. 7 (relative to FIG. 6) so thatthe input facets 612 a-612 d (collectively, 612) on the surface 606 ofthe photonic integrated circuit face a top surface 738 of the opticalwindow 730 of the cap 720.

The optical director element 718 and the collimation lenses 736 (whenpresent) direct the beams of light 610 a-610 d (see FIG. 6) into thephotonic integrated circuit 600 via the input facets 612 a-612 d. Thephotonic integrated circuit 600 may be bonded to the top surface of theoptical window 730, as shown in FIG. 7. In at least someimplementations, the photonic integrated circuit 600 may be bonded tothe top surface 704 of the base substrate 702 instead. As discussedabove, in operation, the photonic integrated circuit 600 receives aplurality of beams of light 610 a-610 d via the input facets 612 a-612 d(e.g. grating couplers), respectively, and wavelength multiplexes theplurality of beams to provide a coaxially superimposed aggregate beam oflight 614 that exits the photonic integrated circuit at the outputoptical coupler 608.

In at least some implementations, the laser diodes 710 may be directlycoupled to the photonic integrated circuit 600. In such implementations,the laser diodes 710 may be positioned immediately adjacent to awaveguide structure (e.g., photonic integrated circuit or otherwaveguide structure) such that sufficient coupling (e.g., acceptableinsertion loss) is achieved. For example, in at least someimplementations, the photonic integrated circuit 600 may function as theoptical window of the package itself.

Following out-coupling of the aggregate beam 614 from the output facet608 of the photonic integrated circuit 600, the aggregated beam may becollimated via the common collimation lens 602. In at least someimplementations, the common collimation lens 602 may be bonded to thetop surface 704 proximate the photonic integrated circuit 600. In atleast some implementations, the collimation lens 602 may be either anachromatic lens or an apochromatic lens, depending on the particularoptical design and tolerances of the system. In at least someimplementations, the optical engine 700 may include one or morediffractive optical elements 604 to provide wavelength dependent focuscorrection.

In at least some implementations, at least some of the components may bepositioned differently. As noted above, the laser diode driver circuit714 may be mounted on the top surface 704 or the bottom surface 706 ofthe base substrate 702, or may be positioned remotely therefrom,depending on the RF design and other constraints (e.g., package size),similarly to as discussed with reference to FIGS. 16A and 16B below. Inat least some implementations, the optical engine 700 may not include anoptical director element (e.g., optical director element 718 of FIG. 7),and the laser light may be directed from the laser diodes 710 toward theoptical window 730 directly, with our without collimation lenses 736.Additionally, in at least some implementations, one or more of the laserdiodes 710 may be mounted directly on the base substrate 702 without useof a submount. Further, in at least some implementations, in the case ofan inorganic or acceptably organic waveguide (e.g., photonic integratedcircuit), coupling may be accomplished inside the encapsulated package.Such feature eliminates the requirement for a separate window, as thewaveguide services as the window (e.g., optical window 730). In suchimplementations, the plurality of grating couplers of the photonicintegrated circuit may be positioned inside the interior volume of theencapsulated package and the at least one optical output coupler of thephotonic integrated circuit may be positioned outside of the interiorvolume, for example.

For the sake of a controlled atmosphere inside the interior volume 732,it may be desirable to have no organic compounds inside the interiorvolume 732. In at least some implementations, the components of theoptical engine 700 may be bonded together using no adhesives. In otherimplementations, a low amount of adhesives may be used to bond at leastone of the components, which may reduce cost while providing arelatively low risk of organic contamination for a determined lifetime(e.g., 2 or more years) of the optical engine 700. Similarly to asdetailed above regarding FIGS. 1A and 1B, partial hermiticity, aparticulate dust cover, or even no protective cover may be acceptablefor certain applications. Various bonding processes (e.g., attachingprocesses) for the optical engine 700 are discussed above with referenceto FIG. 5.

In at least some implementations, the collimation lenses 736 (whenpresent) and the collimation lens 602 may be actively aligned. In atleast some implementations, the CoSs 712, the cap 720 (including opticalwindow 730), and/or the photonic integrated circuit 600 may be passivelyaligned. Further, depending on the particular design, it may beadvantageous to utilize a smaller base substrate 702 and use anadditional carrier substrate instead.

FIG. 8 is a top plan view of a photonic integrated circuit 800 forwavelength multiplexing followed by a common collimation lens 802 and anoptional diffractive optical element 804. The photonic integratedcircuit 800 may be a component in an optical engine, such as an opticalengine 900 of FIG. 9 or an optical engine of FIG. 13 discussed furtherbelow. The photonic integrated circuit 800 includes at least one inputoptical edge 806 having at least one input facet and at least one outputoptical edge 808 having at least one output facet. In the example ofFIG. 8, input edge 806 includes four input facets 806 a, 806 b, 806 c,and 806 d, whereas output edge 808 includes one output facet 808 a.However, it is within the scope of the present systems, devices, andmethods to include any appropriate number of input facets and outputfacets. Similar to the photonic integrated circuit 600 of FIG. 6, inoperation the photonic integrated circuit 800 receives a plurality ofbeams of light 810 a-810 d that are edge coupled to the photonicintegrated circuit at the input optical edge 806, and wavelengthmultiplexes the plurality of beams to provide a coaxially superimposedaggregate beam of light 812 that exits the photonic integrated circuitat the output optical edge 808 through output facet 808 a. Generally,the photonic integrated circuit 800 may include one or more diffractiveoptical elements (DOE) and/or refractive/reflective optical elementsthat combine the different color beams 810 a-810 d in order to achievecoaxial superposition.

Following out-coupling of the aggregate beam 812 from the output opticaledge 808 of the photonic integrated circuit 800, the aggregated beam iscollimated via the common collimation lens 802. In at least someimplementations, the collimation lens 802 may be either an achromaticlens or an apochromatic lens (or lens assemblies), depending on theparticular optical design and tolerances of the system. In at least someimplementations, one or more diffractive optical elements 804 may beused to provide wavelength dependent focus correction.

FIG. 9 is a left side sectional elevational view of the optical engine900. The optical engine 900 includes several components that may besimilar or identical to the components of the optical engine 100 ofFIGS. 1A and 1B. Thus, some or all of the discussion above may beapplicable to the optical engine 900.

The optical engine 900 includes a base substrate 902 having a topsurface 904 and a bottom surface 906 opposite the top surface. The basesubstrate 902 may be formed from a material that is radio frequency (RF)compatible and is suitable for hermetic sealing. For example, the basesubstrate 902 may be formed from low temperature co-fired ceramic(LTCC), alumina, aluminum nitride (AlN), Kovar®, etc.

The optical engine 900 also includes a plurality of chip submounts 908(only one chip submount visible in the sectional view of FIG. 9) thatare bonded (e.g., attached) to the top surface 904 of the base substrate902. The plurality of chip submounts 908 are aligned in a row across awidth of the optical engine 900 between the left and right sidesthereof. Each of the plurality of chip submounts 908 includes a laserdiode 910, also referred to as a laser chip or laser die, bondedthereto. In particular, an infrared chip submount carries an infraredlaser diode, a red chip submount carries a red laser diode, a green chipsubmount carries a green laser diode, and a blue chip submount carries ablue laser diode. In operation, the infrared laser diode providesinfrared laser light, the red laser diode provides red laser light, thegreen laser diode provides green laser light, and the blue laser diodeprovides blue laser light. Each of the laser diodes 910 may comprise oneof an edge emitter laser or a vertical-cavity surface-emitting laser(VCSEL), for example. Each of the four laser diode/chip submount pairsmay be referred to collectively as a “laser chip on submount,” or alaser CoS 912. Thus, the optical engine 900 includes an infrared laserCoS, a red laser CoS, a green laser CoS, and a blue laser CoS. In atleast some implementations, one or more of the laser diodes 910 may bebonded directly to the base substrate 902 without use of a submount 908.

The optical engine 900 also includes a laser diode driver circuit 914bonded to the bottom surface 906 of the base substrate 902. The laserdiode driver circuit 914 is operatively coupled to the plurality oflaser diodes 910 via suitable electrical connections 916 to selectivelydrive current to the plurality of laser diodes. Generally, the laserdiode driver circuit 914 may be positioned relative to the CoSs 912 tominimize the distance between the laser diode driver circuit 914 and theCoSs 912. Although not shown in FIG. 9, the laser diode driver circuit914 may be operatively coupleable to a controller (e.g.,microcontroller, microprocessor, ASIC) that controls the operation ofthe laser diode driver circuit 914 to selectively modulate laser lightemitted by the laser diodes 910. In at least some implementations, thelaser diode driver circuit 914 may be bonded to another portion of thebase substrate 902, such as the top surface 904 of the base substrate,similar to the implementation shown in FIG. 16A. In at least someimplementations, the laser diode driver circuitry 914 may be remotelylocated and operatively coupled to the laser diodes 910, similar to theimplementations shown in FIG. 16B. In order to not require the use ofimpedance matched transmission lines, the size scale may be smallcompared to a wavelength (e.g., lumped element regime), where theelectrical characteristics are described by (lumped) elements likeresistance, inductance, and capacitance.

The optical engine 900 also includes a cap 920 that includes a verticalsidewall 922 and a horizontal wall or top portion 925. The verticalsidewall 922 includes a lower first end 924 and an upper second end 926opposite the first end. A flange 928 may be disposed around a perimeterof the sidewall 922 adjacent the lower first end 924. Within a portionof the vertical sidewall 922 there is an optical window 930 positionedproximate the laser diodes 910 to pass light therefrom out of the cap920. In some implementations, optical window 930 can extend from basesubstrate 902 to top portion 925, such that one side of cap 920 isformed entirely by optical window 930. The sidewall 922 and the opticalwindow 930 together define an interior volume 932 sized and dimensionedto receive the plurality of chip submounts 908 and the plurality oflaser diodes 910. The lower first end 924 and the flange 928 of the cap920 are bonded to the base substrate 902 to provide a hermetic orpartially hermetic seal between the interior volume 932 of the cap and avolume 934 exterior to the cap.

The cap 920 may have a round shape, rectangular shape, or other shape.Thus, the vertical sidewall 922 may comprise a continuously curvedsidewall, a plurality (e.g., four) of adjacent planar portions, etc. Theoptical window 930 may comprise an entire side of the cap 920, or maycomprise only a portion thereof. In at least some implementations, thecap 920 may include a plurality of optical windows instead of a singleoptical window 930.

The optical engine 900 also includes four coupling lenses 936 (only onevisible in the sectional view of FIG. 9), one for each of the four laserdiodes 910 that are bonded to the top surface 904 of the base substrate902 in a row. Each of the plurality of coupling lenses 936 is positionedand oriented to receive light from a corresponding one of the laserdiodes 910 through the optical window 930.

The coupling lenses 936 couple the beams of light 810 a-810 d (see FIG.8) into the photonic integrated circuit 800 via the input optical edge806. The photonic integrated circuit 800 may be bonded to the topsurface 904 of the base substrate 902 proximate the row of couplinglenses 936. As discussed above, in operation, the photonic integratedcircuit 800 receives a plurality of beams of light 810 a-810 d at theinput optical edge 806, and wavelength multiplexes the plurality ofbeams to provide a coaxially superimposed aggregate beam of light 812that exits the photonic integrated circuit at the output optical edge808.

In at least some implementations, the laser diodes 910 may be “butt”coupled to the photonic integrated circuit 800. In such implementations,the laser diodes 910 may be positioned immediately adjacent to awaveguide structure (e.g., photonic integrated circuit or otherwaveguide structure) such that sufficient coupling (e.g., acceptableinsertion loss) is achieved without the use of a coupling lens.

Following out-coupling of the aggregate beam 812 from the output opticaledge 808 of the photonic integrated circuit 800, the aggregated beam maybe collimated via the common collimation lens 802, which may be bondedto the top surface 904 proximate the photonic integrated circuit 800. Inat least some implementations, the collimation lens 802 may be either anachromatic lens or an apochromatic lens, depending on the particularoptical design and tolerances of the system. In at least someimplementations, the optical engine 900 may include one or morediffractive optical elements 804 bonded to the top surface 904 of thebase substrate 902 to provide wavelength dependent focus correction.

In at least some implementations, at least some of the components may bepositioned differently. As noted above, the laser diode driver circuit914 may be mounted on the top surface 904 or the bottom surface 906 ofthe base substrate 902, or may be positioned remotely therefrom,depending on the RF design and other constraints (e.g., package size).In at least some implementations, the optical engine 900 may includeoptical director element (e.g., optical director element 118 of FIG. 1),and the laser light may be directed from the laser diodes 910 toward thecoupling lenses 936 via an intermediate optical director element.Additionally, in at least some implementations, one or more of the laserdiodes 910 may be mounted directly on the base substrate 902 without useof a submount. Further, in at least some implementations, in the case ofan inorganic or acceptably organic waveguide (e.g., photonic integratedcircuit), coupling may be accomplished inside the encapsulated package.Such feature eliminates the requirement for a separate window, as thewaveguide services as the window (e.g., optical window 930). In suchimplementations, the at least one optical input edge of the photonicintegrated circuit may be positioned inside the interior volume of theencapsulated package and the at least one optical output edge of thephotonic integrated circuit may be positioned outside of the interiorvolume, for example.

For the sake of a controlled atmosphere inside the interior volume 932,it may be desirable to have no organic compounds inside the interiorvolume 932. In at least some implementations, the components of theoptical engine 900 may be bonded together using no adhesives. In otherimplementations, a low amount of adhesives may be used to bond at leastone of the components, which may reduce cost while providing arelatively low risk of organic contamination for a determined lifetime(e.g., 2 or more years) of the optical engine 900. Similarly to asdetailed above regarding FIGS. 1A and 1B, partial hermiticity, aparticulate dust cover, or even no protective cover may be acceptablefor certain applications. Various bonding processes (e.g., attachingprocesses) for the optical engine 900 are discussed above with referenceto FIG. 5.

Due to the divergent beam from each of the laser diodes 910 and thelateral distances between the laser diodes, the coupling lenses 936, andthe photonic integrated circuit 800, it may be advantageous to minimizea distance between the respective output facets of the laser diodes 910and the optical window 930. For the same reason, it may be advantageousto minimize the thickness of the optical window 930 and the size of theflange 928 of the cap 920 so that the coupling lenses 936 can bepositioned relatively close to the output facets of the laser diodes910. In at least some implementations, output window 930 and couplinglenses 936 could be formed as a single element.

In at least some implementations, the coupling lenses 936 and thecollimation lens 802 may be actively aligned. In at least someimplementations, the CoSs 912, the cap 920 (including optical window930), and/or the photonic integrated circuit 800 may be passivelyaligned. Further, depending on the particular design, it may beadvantageous to utilize a smaller base substrate 902 and use anadditional carrier substrate instead.

FIG. 10 is a schematic diagram of a laser writing system 1000 inaccordance with the present systems, designs and methods. Laser writingsystem 1000 comprises at least writing laser 1010, focusing optic 1012,writeable glass 1020 and translatable mount 1030. Although the term“glass” is used herein for convenience, any appropriate laser-writablematerial could be used in place of writeable glass 1020, such asorganically modified ceramics (ORMOCER), for example. Writing laser 1010emits laser light 1011. Laser light 1011 comprises short (femptosecondand/or picosecond length) pulses of laser light; consequently, laserlight 1011 has extremely high peak instantaneous power. Focusing optic1012 focuses laser light 1011 to focal point 1013. Writeable glass 1020may comprise a contiguous piece of glass or similar transparentmaterial, which is typically transparent to the laser light 1011 emittedby the writing laser 1010; in other words the light emitted by thewriting laser generally will not be absorbed by the glass via typical(linear) optical processes. At the focal point 1013, the intensity oflaser light 1011 is very high due to the combination of spatial focusing(focusing the beam of writing laser light 1011 to a small point 1013)and temporal focusing (emitting the laser light 1011 as extremely shortfemptosecond or picosecond pulses). The high intensity of light at thefocal point 1013 allows nonlinear optical processes such as multiphotonabsorption, avalanche ionization, Coulomb collisions (causing latticeionization and breakdown), and heat conduction to occur in the writeableglass 1020, absorbing the light and changing the refractive index of theglass. The change in refractive index may be a positive increase inrefractive index.

Writeable glass 1020 can be physically coupled to translatable mount1030, such as by using clamps 1021, adhesive, or any other appropriatecoupling mechanism. Such coupling mechanism is preferably removable,such that writeable glass 1020 can be detached from translatable mount1030 after laser writing is complete. Translation of translatable mount1030 in the X, Y, and/or Z direction will result in correspondingtranslation of writeable glass 1020, moving the location of focal point1013 within writeable glass 1020. Translating the writeable glass 1020relative to focal point 1013 can create a region of changed refractiveindex in the writeable glass 1020. An increased refractive index in thisregion causes any light channeled therethrough to experience totalinternal reflection, thus forming waveguide 1022. In other words,waveguide 1022 can be formed as a continuous path of increasedrefractive index within writeable glass 1020 created by laser light 1011at focal point 1013.

The technique of FIG. 10 can be used to laser write at least onewaveguide into writeable glass 1020. For example, a photonic integratedcircuit could be written, such as photonic integrated circuit 600described with regards to FIG. 6 or photonic integrated circuit 800described with regards to FIG. 8. Inputs facets 612 a, 612 b, 612 c, and612 d (such as grating couplers), or input facets 806 a, 806 b, 806 c,and 806 d could also be written using this technique.

Writing at least one waveguide may include writing an individualwaveguide for each wavelength of light impinging on the writeable glass1020, where each waveguide comprises a respective input facet (such asan input grating coupler) and a respective output facet. Each outputfacet may be positioned to provide light to other components or modules,such as a scan mirror of a laser projector, etc. In one implementation,four waveguides could be written into writeable glass 1020, onewaveguide for each beam of light 610 a, 610 b, 610 c, and 610 d. Fourgrating couplers could also be written, one for each waveguide. Inanother implementation, four waveguides could be written into writeableglass 1020, one waveguide for each beam of light 810 a, 810 b, 810 c,and 810 d.

Writing at least one waveguide may include writing a waveguide combiner,wherein the waveguide combiner combines individual laser beams into acoaxially superimposed aggregate beam. Writing a waveguide combiner mayinclude writing at least one: directional coupler (DC), Y-branch,whispering gallery mode coupler, or multi-mode interference coupler. Theaggregate beam may be provided to other components or modules, such as ascan mirror of a laser projector, etc.

In other implementations, the photonic integrated circuit 600 or thephotonic integrated circuit 800 may include one or more diffractiveoptical elements (DOE) and/or refractive/reflective optical elementsthat combine the different color beams 610 a-d or 810 a-d in order toachieve coaxial superposition.

Alternatively, instead of writing a waveguide combiner, individualwaveguides could be written which do not strictly coaxially superimposethe beams of light, but instead bring each beam of light close together.That is, the input facet (e.g. grating coupler) for each waveguide inthe photonic integrated circuit can be positioned relatively far fromthe other input facets, to receive laser light from a respective laserdiode, but the output facets for each of the waveguides can bepositioned relatively close together. In other words, a spacing betweenthe output facets of each waveguide can be smaller than a spacing of theinput facets of each waveguide. In such an implementation, eachwaveguide can be optimized for performance with light of a correspondingwavelength, for example to ensure that each wavelength of light exitsthe photonic integrated circuit with the same divergence angle as eachother wavelength. The output of each individual waveguide can be placedclose enough together (on the order of 1 Os of microns) such that thatthe light output by each individual waveguide may still follow the sameoptical path through the rest of a projector, display, or WHUD assemblywhere the photonic integrated circuit is implemented.

FIG. 11 is a flow diagram of a method 1100 of manufacturing an opticalengine, in accordance with the present systems, devices, and methods.The method 1100 may be implemented to manufacture the optical engine 700of FIG. 7 or the optical engine 900 of FIG. 9, for example. It should beappreciated that methods of manufacturing optical engines according tothe present disclosure may include fewer or additional acts than setforth in the method 1100. Further, the acts discussed below may beperformed in an order different than the order presented herein.

Method 1100 can include at least acts 1102, 1104, 1106, 1108, 1110,1112, 1114, and 1116. Acts 1102, 1104, 1106, 1108, and 1110substantially correspond to acts 502, 504, 506, 508, and 510,respectively, of method 500 in FIG. 5, such that the disclosure of theseacts with reference to FIG. 5 is also applicable to FIG. 11. As such,the details of these acts in FIG. 11 will not be repeated in theinterests of brevity.

At 1112, a photonic integrated circuit is laser written in writeableglass, using for example the techniques described with regards to FIG.10. The photonic integrated circuit may be similar to photonicintegrated circuit 600 described with reference to FIG. 6 or photonicintegrated circuit 800 described with reference to FIG. 8. Specifically,the photonic integrated circuit can include at least one input facet andat least one output facet. In operation, the photonic integrated circuitcan receive a plurality of beams of light that are coupled to thephotonic integrated circuit at a plurality of input facets (e.g. gratingcouplers), and wavelength multiplex the plurality of beams of light toprovide a coaxially superimposed aggregate beam of light that exits thephotonic integrated circuit at the output facet. Alternatively, inoperation, the photonic integrated circuit can receive a plurality ofbeams of light that are coupled to the photonic integrated circuit at aplurality of input facets (e.g. grating couplers), redirect theplurality of beams of light to exit the photonic integrated circuit at aplurality of spatially close output facets.

At 1114, the writeable glass including the photonic integrated circuitis bonded to the cap or the base substrate. Any appropriate bondingtechnique may be used, including those described with reference to acts502, 504, 506, 508, and 510 in FIG. 5. In some implementations, thephotonic integrated circuit may be positioned against an optical windowof the cap, such that laser light from the laser diodes may pass throughthe optical window directly into the input facets of the photonicintegrated circuit. Alternatively, the photonic integrated circuit maybe positioned directly against the cap, such that the photonicintegrated circuit acts as the optical window, and laser light from thelaser diodes may directly enter the input facets of the photonicintegrated circuit. In other implementations, the photonic integratedcircuit may be spatially separated from the cap.

In order for light to travel through a photonic integrated circuit, thelight emitted by each laser diode should preferably be aligned with arespective input facet of the photonic integrated circuit with highprecision; mis-alignment of greater than 10 micrometers maysignificantly reduce the efficiency of the photonic integrated circuit.An output facet of each laser diode may have dimensions smaller thanfour square micrometers; aligning such small components to such highprecision presents a non-trivial technical challenge.

In one implementation, each input facet of the photonic integratecircuit could be written as a grating coupler as shown in FIG. 6, whichincreases the tolerances for misalignment.

In act 1116, a collimation lens may be provided such that a coaxiallysuperimposed beam of light from the output edge of the photonicintegrated circuit will be collimated by the collimation lens. Thecollimation lens may optionally optimize the spot (e.g., circularize)the coaxially superimposed beam. In some implementations, more than onecollimation lens may be provided if the light output from the photonicintegrated circuit is not a fully coaxially superimposed beam. Thecollimation lens or lenses may be actively aligned after the othercomponents are assembled, or may be passively aligned such thatappropriate alignment is achieved during assembly.

As mentioned above, aligning a photonic integrated circuit such thateach input facet of the photonic integrated circuit lines up with a beamof light emitted by each laser diode with high-precision presents anon-trivial challenge. The present systems, devices, and methods providea solution to this challenge, by producing photonic integrated circuitswhere the fabrication process includes an alignment process, obviatingthe need for a later mechanical alignment process, as discussed belowwith reference to FIGS. 12, 12B, and 13. Direct laser writing (DLW) asdisclosed herein is a process by which photonic integrated circuits maybe fabricated with high precision that allows for intrinsic alignment.

FIG. 12A is a left side sectional view of photonic integrated circuitwriting system 1200 a. Photonic integrated circuit writing system 1200 aincludes components that may be substantively similar to components ofoptical engine 700 and components of laser writing system 1000. Unlesscontext below dictates otherwise, the disclosure of components in FIG. 7and FIG. 10 is applicable to similarly numbered components in FIG. 12Aand will not be repeated in the interests of brevity. Photonicintegrated circuit writing system 1200 a includes laser writing system1000, which, during operation, writes a photonic integrated circuit in ablock of writeable glass 1020 in a manner similar to the operation oflaser writing system 1000 described above with reference to FIG. 10.Photonic integrated circuit writing system 1200 a can be utilized tomanufacture an optical engine using a process that is similar in atleast some respects to method 1100 of FIG. 11, but with photonicintegrated circuit writing system 1200 a, act 1114 can be performedbefore act 1112, as detailed below.

Writeable glass 1020 is bonded to cap 720 prior to writing a photonicintegrated circuit therein, using any of the bonding techniquesdiscussed above. The writeable glass 1020 may comprise a contiguouspiece of glass or similar transparent material that undergoes a changein refractive index when exposed to high-intensity laser light. Bondingthe writeable glass to the cap includes positioning and orienting thewriteable glass 1020 relative to each laser diode 710 to place thewriteable glass 1020 in the path of the beam of light emitted by eachlaser diode 710, such that the beam of light emitted by each laser diode710 impinges on the writeable glass.

Writeable glass 1020 can be positioned against optical window 730, suchthat beams of light from laser diodes 710 pass through optical window730 directly into writeable glass 1020. Alternatively, the writeableglass 1020 may optionally form optical window 730.

The entire base substrate 702 and all components bonded thereto can bephysically coupled to translatable mount 1030, such as with clamps 1021,adhesives, and/or any other appropriate coupling mechanism. Suchcoupling mechanism is preferably removable, such that base substrate 702and all components bonded thereto can be detached from translatablemount 1030 after laser writing of writeable glass 1020 is complete.

With writeable glass 1020 bonded indirectly to base substrate 702 viacap 720, and base substrate 702 physically coupled to translatable mount1030, at least one waveguide 1022 can be laser written into writeableglass 1020 by translating base substrate 702 and all components thereonusing translatable mount 1030. At least one input facet 612 (for exampleat least one grating input coupler) can also be written into writeableglass 1020 by translating base substrate 702 and all components thereonusing translatable mount 1030. Consequently, writeable glass 1020becomes a photonic integrated circuit.

To determine where the at least one waveguide 1022 should be written,laser diodes 710 could be activated, thus causing beams of lighttherefrom to impinge on writeable glass 1020. Writing laser 1010 can bealigned to directly write waveguides and input facets (e.g. gratingcouplers as shown in FIG. 12A) at the exact location where the beams oflight from laser diodes 710 impinge on the writeable glass 1020. In thisway, the input facets of the resulting photonic integrated circuit willbe accurately aligned with the laser diodes, ensuring efficientincoupling of the beams of light into the photonic integrated circuit.

Alternatively, the writeable glass 1020 could be illuminated, such as bybeing backlit if base substrate 702 is at least partially transparent.Writing laser 1010 can then be aligned to directly write waveguidesbased on locations of shadows caused by laser diodes 710, CoS's 712 andoptical redirector element 718. In this way, the input facets of theresulting photonic integrated circuit will be accurately aligned withthe laser diodes, ensuring efficient incoupling of the beams of lightinto the photonic integrated circuit.

Aligning the input facets of the photonic integrated circuit to thebeams of light during the writing stage will be more accurate thantrying to mechanically align a pre-fabricated photonic integratedcircuit, due to deviations that can arise in the bonding processes ofnot only the pre-fabricated photonic integrate circuit, but also thelaser diodes. As one example, if each of four laser diodes is randomlymisaligned, it would be difficult to align a prefabricated photonicintegrated circuit to match the beam of light from each diode, since notonly could the photonic integrated circuit be misaligned during thebonding processes, but also the spacing between each laser diode may notmatch the spacing between each waveguide in the photonic integratedcircuit due to the random misalignment of each of the laser diodes.Direct laser writing the photonic integrated circuit after all of thecomponents have been mechanically bonded obviates these issues, byallowing the position and spacing of each laser diode relative to thewriteable glass to be accounted for after bonding is complete.

FIG. 12B is a left side sectional view of photonic integrated circuitwriting system 1200 b. Photonic integrated circuit writing system 1200 bincludes components that may be substantively similar to components ofphotonic integrated circuit writing system 1200 a as discussed withregards to FIG. 12A. Unless context below dictates otherwise, thedisclosure related to components in FIG. 12A is applicable to similarlynumbered components in FIG. 12B and will not be repeated in theinterests of brevity.

In FIG. 12B, instead of writing the input facets 612 of the photonicintegrated circuit 600 as grating input couplers, a reflective surfaceis instead written to redirect input beams of light 610 into at leastone waveguide 1022 of photonic integrated circuit 600. For example, theat least one reflective surface could be a planar region with lowerindex of refraction than the material from which writeable glass 1020 isformed. Consequently, laser light 610 can be redirected by the planarregion with lower index of refraction due to total internal reflection.

Additionally, FIG. 12B illustrates an implementation in which at leastone laser diode 710 is a vertical-cavity surface-emitting laser (VCSEL),such that laser light emitted by the laser diode is directed towardsoptical window 730 without the need for an optical redirecting element.Such a laser diode setup could be implemented in any of theimplementations discussed herein. The implementation of FIG. 12B doesnot require the use of a VCSEL, but could instead use a side emittinglaser with an optical redirecting element such as shown in FIGS. 1A and1B.

FIG. 13 is a left side sectional view of photonic integrated circuitwriting system 1300. Photonic integrated circuit writing system 1300includes components that may be substantively similar to components ofoptical engine 900 and components of laser writing system 1000. Unlesscontext below dictates otherwise, the disclosure of components in FIG. 9and FIG. 10 is applicable to similarly numbered components in FIG. 13and will not be repeated in the interests of brevity. Photonicintegrated circuit writing system 1300 includes laser writing system1000, which, during operation, writes a photonic integrated circuit in ablock of writeable glass 1020 in a manner similar to the operation oflaser writing system 1000 described above with reference to FIG. 10.Photonic integrated circuit writing system 1300 can be utilized tomanufacture an optical engine using a process that is similar in atleast some respects to method 1100 of FIG. 11, but with photonicintegrated circuit writing system 1300, act 1114 can be performed beforeact 1112, as detailed below.

Writeable glass 1020 is bonded to base substrate 902 prior to writing aphotonic integrated circuit therein, using any of the bonding techniquesdiscussed above. The writeable glass 1020 may comprise a contiguouspiece of glass or similar transparent material that undergoes a changein refractive index when exposed to high-intensity laser light. Bondingthe writeable glass to the base substrate includes positioning andorienting the writeable glass 1020 relative to each laser diode 910 toplace the writeable glass 1020 in the path of the beam of light emittedby each laser diode 910, such that the beam of light emitted by eachlaser diode 910 impinges on an input edge of the writeable glass.

Writeable glass 1020 can be butted up against optical window 930, suchthat beams of light from laser diodes 910 passes through optical window930 directly into writeable glass 1020. Alternatively, the writeableglass 1020 may optionally form optical window 930. Further, writeableglass 1020 may be bonded directly to at least one of the laser diodes910 and/or at least one laser CoS 912.

The entire base substrate 902 and all components bonded thereto can bephysically coupled to translatable mount 1030, such as with clamps 1021,adhesives, and/or any other appropriate coupling mechanism. Suchcoupling mechanism is preferably removable, such that base substrate 902and all components bonded thereto can be detached from translatablemount 1030 after laser writing of writeable glass 1020 is complete.

With writeable glass 1020 bonded to base substrate 902 and basesubstrate 902 physically coupled to translatable mount 1030, at leastone waveguide 1022 can be laser written into writeable glass 1020 bytranslating base substrate 902 and all components thereon usingtranslatable mount 1030. Consequently, writeable glass 1020 becomes aphotonic integrated circuit.

To determine where the at least one waveguide 1022 should be written,laser diodes 910 could be activated, thus causing beams of lighttherefrom to impinge on an input edge of writeable block 1020. Writinglaser 1010 can be aligned to directly write waveguides at the exactlocation where the beams of light from laser diodes 910 impinge on thewriteable block 1020. In this way, the input of the resulting photonicintegrated circuit will be accurately aligned with the laser diodes,ensuring efficient incoupling of the beams of light into the photonicintegrated circuit.

Alternatively, the writeable glass 1020 could be illuminated, such as bybeing backlit if base substrate 902 is at least partially transparent.Writing laser 1010 can then be aligned to directly write waveguides atlocations where shadows of laser diodes 910 and/or CoS's 912 appear. Inthis way, the input of the resulting photonic integrated circuit will beaccurately aligned with the laser diodes, ensuring efficient incouplingof the beams of light into the photonic integrated circuit.

Aligning the input facets of the photonic integrated circuit to thebeams of light during the writing stage will be more accurate thantrying to mechanically align a pre-fabricated photonic integratedcircuit, due to deviations that can arise in the bonding processes ofnot only the pre-fabricated photonic integrate circuit, but also thelaser diodes. As one example, if each of four laser diodes is randomlymisaligned, it would be difficult to align a prefabricated photonicintegrated circuit to match the beam of light from each diode, since notonly could the photonic integrated circuit be misaligned during thebonding processes, but also the spacing between each laser diode may notmatch the spacing between each waveguide in the photonic integratedcircuit due to the random misalignment of each of the laser diodes.Direct laser writing the photonic integrated circuit after all of thecomponents have been mechanically bonded obviates these issues, byallowing the position and spacing of each laser diode relative to thewriteable glass to be accounted for after bonding is complete.

In some implementations, a photonic integrated circuit could bemanufactured using a combination of the techniques described withreference to FIGS. 10, 11, 12A, 12B, and 13 as discussed below.

In one example, a large portion of a photonic integrated circuit couldbe first written, except for a small portion of the photonic integratedcircuit at the input of writeable glass. Subsequently, the photonicintegrated circuit could be bonded to the cap or the base substrate suchas in FIG. 12A, 12B, or 13, and the remaining small portion of thephotonic integrated circuit at the input of the writeable glass could bewritten to couple the output of each laser diode to the portion of thephotonic integrated circuit which is already written.

In another example, a first photonic integrated circuit could be writtenas in FIG. 10. Subsequently, the first photonic integrated circuit couldbe bonded to the cap similar to as in FIG. 7, 12A, or 12B, or to thebase substrate as in FIG. 9 or 13, with the first photonic integratedcircuit being spatially separated from the output of each laser diodesuch that there is a gap between the output from each laser diode andthe first photonic integrated circuit. In the area in the output path ofeach laser diode, a block of writeable glass could be bonded to the capor to the base substrate in the gap between the output from each laserdiode and the first photonic integrated circuit. Subsequently, a secondphotonic integrated circuit could be written in the writeable glasssimilar to in FIGS. 12A, 12B, and 13 to couple the output of each laserdiode to an input edge of the previously written first photonicintegrated circuit. In such an example, the writeable glass could beformed as the optical window, and/or could be formed to cover a portionof the first photonic integrated circuit. FIGS. 14 and 15 illustrateexemplary implementations of this setup.

FIG. 14 is a left side sectional elevational view of a portion of anoptical engine 1400. The optical engine 1400 includes several componentsthat may be similar or identical to the components of the opticalengines 100, 700 or 900. Thus, some or all of the discussion above maybe applicable to the optical engine 1400, and is not repeated herein forthe sake of brevity. For example, portions of the optical engine 1400not shown in FIG. 14 may be similar or identical to correspondingportions of the optical engine 900 of FIG. 9.

The optical engine 1400 includes a base substrate 1402 having a topsurface 1404 and a bottom surface (not shown) opposite the top surface.The base substrate 1402 may be formed from a material that is radiofrequency (RF) compatible and is suitable for hermetic sealing. Forexample, the base substrate 1402 may be formed from low temperatureco-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, etc.

The optical engine 1400 also includes a plurality of chip submounts 1408(only one chip submount visible in the sectional view of FIG. 14) thatare bonded (e.g., attached) to the top surface 1404 of the basesubstrate 1402. The plurality of chip submounts 1408 are aligned in arow across a width of the optical engine 1400 between the left and rightsides thereof. Each of the plurality of chip submounts 1408 includes alaser diode 1410, also referred to as a laser chip or laser die, bondedthereto. In particular, an infrared chip submount carries an infraredlaser diode, a red chip submount carries a red laser diode, a green chipsubmount carries a green laser diode, and a blue chip submount carries ablue laser diode. In operation, the infrared laser diode providesinfrared laser light, the red laser diode provides red laser light, thegreen laser diode provides green laser light, and the blue laser diodeprovides blue laser light. Each of the laser diodes 1410 may compriseone of an edge emitter laser or a vertical-cavity surface-emitting laser(VCSEL), for example. Each of the four laser diode/chip submount pairsmay be referred to collectively as a “laser chip on submount,” or alaser CoS 1412. Thus, the optical engine 1400 includes an infrared laserCoS, a red laser CoS, a green laser CoS, and a blue laser CoS. In atleast some implementations, one or more of the laser diodes 1410 may bebonded directly to the base substrate 1402 without use of a submount1408.

Although not shown in FIG. 14, the optical engine 1400 also includes alaser diode driver circuit (e.g., similar or identical to the laserdiode driver circuit 914) bonded to a surface of the base substrate 1402or located remotely therefrom. The laser diode driver circuit 1414 isoperatively coupled to the plurality of laser diodes 1410 via suitableelectrical connections 1416 to selectively drive current to theplurality of laser diodes. Generally, the laser diode driver circuit1414 may be positioned relative to the CoSs 1412 to minimize thedistance between the laser diode driver circuit 1414 and the CoSs 1412.Although not shown in FIG. 14, the laser diode driver circuit 1414 maybe operatively coupleable to a controller (e.g., microcontroller,microprocessor, ASIC) that controls the operation of the laser diodedriver circuit 1414 to selectively modulate laser light emitted by thelaser diodes 1410. In at least some implementations, the laser diodedriver circuit 1414 may be bonded to another portion of the basesubstrate 1402, such as the top surface 1404 of the base substrate. Inat least some implementations, the laser diode driver circuitry 1414 maybe remotely located and operatively coupled to the laser diodes 1410. Inorder to not require the use of impedance matched transmission lines,the size scale may be small compared to a wavelength (e.g., lumpedelement regime), where the electrical characteristics are described by(lumped) elements like resistance, inductance, and capacitance.Exemplary placements for laser diode driver circuitry are describedbelow with reference to FIGS. 16A and 16B.

In at least some implementations, the optical engine 1400 also includesa cap 1420 that includes a vertical sidewall 1422 and a horizontal wallor top portion 1425. The vertical sidewall 1422 includes a lower firstend 1424 and an upper second end 1426 opposite the first end. A flange1428 may be disposed around a perimeter of the sidewall 1422 adjacentthe lower first end 1424. Within a portion of the vertical sidewall 1422there is an optical window 1430 positioned proximate the laser diodes1410 to pass light therefrom out of the cap 1420. The sidewall 1422 andthe optical window 1430 together define an interior volume 1432 sizedand dimensioned to receive the plurality of chip submounts 1408 and theplurality of laser diodes 1410. The lower first end 1424 and the flange1428 of the cap 1420 are bonded to the base substrate 1402 to provide ahermetic or partially hermetic seal between the interior volume 1432 ofthe cap and a volume 1434 exterior to the cap.

The cap 1420 may have a round shape, rectangular shape, or other shape.Thus, the vertical sidewall 1422 may comprise a continuously curvedsidewall, a plurality (e.g., four) of adjacent planar portions, etc. Theoptical window 1430 may comprise an entire side of the cap 1420, or maycomprise only a portion thereof. In at least some implementations, thecap 1420 may include a plurality of optical windows instead of a singleoptical window 1430.

The optical engine 1400 also includes a waveguide medium or material1460 disposed on the top surface 1404 of the base substrate 1404 betweenthe optical window 1430 of the cap 1420 and a photonic integratedcircuit 1450. The waveguide medium 1460 includes waveguides 1462 (e.g.,four waveguides, only one visible in the sectional view of FIG. 14) thatare operative to couple the plurality of beams of light emitted by theplurality of laser diodes 1410 from the optical window 1430 of the cap1420 to input couplers (e.g., edge couplers, grating couplers) on anedge 1452 or top surface 1454 of the photonic integrated circuit 1450.Each of the plurality of waveguides 1462 is positioned and dimensionedto receive light from a corresponding one of the laser diodes 1410through the optical window 1430. The waveguides 1462 may be directlywritten using the direct laser writing process described above withreference to FIG. 10, 11, 12A, 12B, or 13, or any other suitableprocess.

The waveguides 1462 couple the beams of light into the photonicintegrated circuit 1450 via input optical edge couplers or gratingcouplers. The photonic integrated circuit 1450 may be bonded to the topsurface 1404 of the base substrate 1402 proximate the waveguide medium1460. As discussed above, in operation, the photonic integrated circuit1450 receives a plurality of beams of light at the input couplers, andwavelength multiplexes the plurality of beams to provide a coaxiallysuperimposed aggregate beam of light that exits the photonic integratedcircuit at an output optical edge.

In at least some implementations, at least some of the components may bepositioned differently. As noted above, a laser diode driver circuitoperatively coupled to the laser diodes 1410 may be mounted on the topsurface 1404 or the bottom surface of the base substrate 1402, or may bepositioned remotely therefrom, depending on the RF design and otherconstraints (e.g., package size). In at least some implementations, theoptical engine 1400 may include optical director element (e.g., opticaldirector element 118 of FIG. 1), and the laser light may be directedfrom the laser diodes 1410 toward the waveguide medium 1460 via anintermediate optical director element. In at least some implementations,photonic integrated circuit 1450 and waveguide medium 1460 may bepositioned on top of cap 1420, and the optical window 1430 may be in topportion 1425 of cap 1420, with light beams from laser diodes 1410passing through the optical window 1430 on the top portion of cap 1420into waveguide medium 1460 and subsequently photonic integrated circuit1450. Additionally, in at least some implementations, one or more of thelaser diodes 1410 may be mounted directly on the base substrate 1402without use of a submount. Further, in at least some implementations, inthe case of an inorganic or acceptably organic waveguide, coupling maybe accomplished inside the encapsulated package. Such feature eliminatesthe requirement for a separate window, as the waveguide medium 1460services as the window (e.g., optical window 1430). In suchimplementations, the at least one optical input coupler of the photonicintegrated circuit may be positioned inside the interior volume of theencapsulated package and the at least one optical output edge of thephotonic integrated circuit may be positioned outside of the interiorvolume, for example.

In at least some implementations, the waveguides 1462 may be directlywritten into the waveguide medium 1460 using any suitable direct writingprocess, such as that described above with reference to FIGS. 10, 12A,12B, and 13. The waveguide medium 1460 may comprise any suitablephotosenstive material. In at least some implementations, the waveguidemedium comprises organically modified ceramic (ORMOCER) material, forexample. As noted above, coupling to the photonic integrated circuit1450 may be done either via edge coupling or grating coupling.

In the illustrated implementation, the written waveguide 1462 and medium1460 is spaced apart from the optical window 1430, and a lens shapedsurface 1464 is formed in the medium 1460. The lens shaped surface 1464may be sized, dimensioned and oriented to couple beams of light from thelaser diodes 1410 into the waveguides 1462 of the waveguide medium 1460.In other implementations, the waveguide 1462 and or waveguide medium1460 may be positioned adjacent (e.g., in contact with) at least one ofthe optical window 1430 of the cap 1430 or the photonic integratedcircuit 1450.

FIG. 15 shows a left side sectional elevational view of a portion of anoptical engine 1500. The optical engine 1500 includes several componentsthat may be similar or identical to the components of the opticalengines 100, 700, 900, or 1400. Thus, some or all of the discussionabove may be applicable to the optical engine 1500, and is not repeatedherein for the sake of brevity. For example, portions of the opticalengine 1500 not shown in FIG. 15 may be similar or identical tocorresponding portions of the optical engine 900 of FIG. 9.

The optical engine 1500 includes a base substrate 1502 having a topsurface 1504 and a bottom surface (not shown) opposite the top surface.The base substrate 1502 may be formed from a material that is radiofrequency (RF) compatible and is suitable for hermetic sealing. Forexample, the base substrate 1502 may be formed from low temperatureco-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, etc.

The optical engine 1500 also includes a plurality of chip submounts 1508(only one chip submount visible in the sectional view of FIG. 15) thatare bonded (e.g., attached) to the top surface 1504 of the basesubstrate 1502. The plurality of chip submounts 1508 are aligned in arow across a width of the optical engine 1500 between the left and rightsides thereof. Each of the plurality of chip submounts 1508 includes alaser diode 1510, also referred to as a laser chip or laser die, bondedthereto. In particular, an infrared chip submount carries an infraredlaser diode, a red chip submount carries a red laser diode, a green chipsubmount carries a green laser diode, and a blue chip submount carries ablue laser diode. In operation, the infrared laser diode providesinfrared laser light, the red laser diode provides red laser light, thegreen laser diode provides green laser light, and the blue laser diodeprovides blue laser light. Each of the laser diodes 1510 may compriseone of an edge emitter laser or a vertical-cavity surface-emitting laser(VCSEL), for example. Each of the four laser diode/chip submount pairsmay be referred to collectively as a “laser chip on submount,” or alaser CoS 1512. Thus, the optical engine 1500 includes an infrared laserCoS, a red laser CoS, a green laser CoS, and a blue laser CoS. In atleast some implementations, one or more of the laser diodes 1510 may bebonded directly to the base substrate 1502 without use of a submount1508.

Although not shown in FIG. 15, the optical engine 1500 also includes alaser diode driver circuit (e.g., similar or identical to the laserdiode driver circuit 914) bonded to a surface of the base substrate 1502or located remotely therefrom, similarly to as described with regards toFIGS. 16A and 16B below. The laser diode driver circuit 1514 isoperatively coupled to the plurality of laser diodes 1510 via suitableelectrical connections 1516 to selectively drive current to theplurality of laser diodes.

The optical engine 1500 also includes a photonic integrated circuit 1550bonded to the top surface 1504 of the base substrate 1502 proximatefacets 1511 of the laser diodes 1510. In operation, the photonicintegrated circuit 1550 receives a plurality of beams of light at inputcouplers (e.g., edge couplers, grating couplers), and wavelengthmultiplexes the plurality of beams to provide a coaxially superimposedaggregate beam of light that exits the photonic integrated circuit at anoutput optical edge (not shown in FIG. 15).

In the illustrated implementation, the laser CoSs 1512 and electricalconnections 1516 (e.g., wirebonds) are covered with a waveguide andsealing medium 1560, which may also cover at least a portion of an edge1552 and a top surface 1554 of the photonic integrated circuit 1550.Advantageously, the waveguide and sealing medium acts as a sealingmaterial for the laser CoSs 1512, eliminating the need for a separatecap (e.g., cap 1420 of FIG. 14) to provide a hermetically or partiallyhermetically sealed package.

The waveguide medium 1560 includes directly written waveguides 1562(e.g., four waveguides, only one visible in the sectional view of FIG.15) that are operative to couple the plurality of beams of light emittedat the facets 1511 of the plurality of laser diodes 1510 to inputcouplers (e.g., edge couplers, grating couplers) on the edge 1552 or topsurface 1554 of the photonic integrated circuit 1550. Each of theplurality of waveguides 1562 is positioned and dimensioned to receivelight from a corresponding one of the laser diodes 1510. The waveguides1562 may be directly written using any suitable process, such as directlaser writing as described with reference to FIGS. 10, 12A, 12B, and 13above.

The waveguides 1562 couple the beams of light into the photonicintegrated circuit 1550 via an input optical edge couplers or gratingcouplers. The photonic integrated circuit 1550 may be bonded to the topsurface 1504 of the base substrate 1502 proximate the waveguide medium1560. As discussed above, in operation, the photonic integrated circuit1550 receives a plurality of beams of light at the input couplers, andwavelength multiplexes the plurality of beams to provide a coaxiallysuperimposed aggregate beam of light that exits the photonic integratedcircuit at an output optical edge.

In at least some implementations, photonic integrated circuit 1550 maybe positioned above laser diodes 1510, and waveguide and sealing medium1560 may be formed to cover laser diodes 1510 and photonic integratedcircuit 1550. At least one waveguide 1562 can be directly written inwaveguide medium 1560 to couple beams of light emitted by laser diodes1510 to input couplers on photonic integrated circuit 1550, using forexample the techniques discussed above regarding FIGS. 10, 12A, 12B, and13.

Although several different materials may be used for direct waveguidewriting, in at least some implementations, an ORMOCER material may beused which is tailored to the particular needs concerning writing aswell as transmission wavelengths.

FIGS. 16A and 16B are isometric views showing implementations of opticalengines having differing positions for a laser diode driver circuit. Theimplementations shown in FIGS. 16A and 16B are similar in at least somerespects to the implementations of FIGS. 1A, 1B, 7, 9, 12A, 12B, 13, 14,and 15, and one skilled in the art will appreciate that the descriptionregarding FIGS. 1A, 1B, 7, 9, 12A, 12B, 13, 14, and 15 are applicable tothe implementations of FIGS. 16A and 16B unless context clearly dictatesotherwise.

FIG. 16A shows an optical engine 1600 a which includes a base substrate1602. The base substrate 1602 may be formed from a material that isradio frequency (RF) compatible and is suitable for hermetic sealing.For example, the base substrate 1602 may be formed from low temperatureco-fired ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar®, etc.

The optical engine 1600 a also includes a plurality of laser diodesaligned in a row across a width of the optical engine 1600 a, includingan infrared laser diode 1610 a, a red laser diode 1610 b, a green laserdiode 1610 c, and a blue laser diode 1610 d. In operation, the infraredlaser diode 1610 a provides infrared laser light, the red laser diode1610 b provides red laser light, the green laser diode 1610 c providesgreen laser light, and the blue laser diode 1610 d provides blue laserlight. Each of the laser diodes may comprise one of an edge emitterlaser or a vertical-cavity surface-emitting laser (VCSEL), for example.In FIG. 16A, laser diodes 1610 a, 1610 b, 1610 c, and 1610 d are shownas being bonded (e.g., attached) directly to base substrate 1602, asdescribed above with regards to act 504 in FIG. 5, but one skilled inthe art will appreciate that laser diodes 1610 a, 1610 b, 1610 c, and1610 d could each be mounted on a respective submount, similar to as inFIGS. 1A and 1B.

The optical engine 1600 a also includes a laser diode driver circuit1614 which can be bonded to the same surface of base substrate 1602 asthe laser diodes 1610 a, 1610 b, 1610 c, 1610 d. In alternativeimplementations, laser diode driver circuit 1614 can be bonded to aseparate base substrate, such as in FIG. 16B discussed later. The laserdiode driver circuit 1614 is operatively coupled to the plurality oflaser diodes 1610 a, 1610 b, 1610 c, and 1610 d via respectiveelectrical connections 1616 a, 1616 b, 1616 c, 1616 d to selectivelydrive current to the plurality of laser diodes. In at least someimplementations, the laser diode driver circuit 1614 may be positionedrelative to the laser diodes 1610 a, 1610 b, 1610 c, and 1610 d tominimize the distance between the laser diode driver circuit 1614 andthe laser diodes. Although not shown in FIG. 16A, the laser diode drivercircuit 1614 may be operatively coupleable to a controller (e.g.,microcontroller, microprocessor, ASIC) which controls the operation ofthe laser diode driver circuit 1614 to selectively modulate laser lightemitted by the laser diodes 1610 a, 1610 b, 1610 c, and 1610 d. In atleast some implementations, the laser diode driver circuit 1614 may bebonded to another portion of the base substrate 1602, such as the bottomsurface of the base substrate 1602. In at least some implementations,the laser diode driver circuitry 1614 may be remotely located andoperatively coupled to the laser diodes 1610 a, 1610 b, 1610 c, and 1610d. In order to not require the use of impedance matched transmissionlines, the size scale may be small compared to a wavelength (e.g.,lumped element regime), where the electrical characteristics aredescribed by (lumped) elements like resistance, inductance, andcapacitance.

Proximate the laser diodes 1610 a, 1610 b, 1610 c, and 1610 d there isoptionally positioned an optical director element 1618. Like the laserdiodes 1610 a, 1610 b, 1610 c, and 1610 d, the optical director element1618 is bonded to the top surface of the base substrate 1602. Theoptical director element 1618 may be bonded proximate to or adjacenteach of the laser diodes 1610 a, 1610 b, 1610 c, and 1610 d. In theillustrated example, the optical director element 1618 has a triangularprism shape that includes a plurality of planar faces, similar tooptical director element 168 in FIGS. 1A and 1B. The optical directorelement 1618 may comprise a mirror or a prism, for example.

The optical engine 1600 a also includes a cap 1620 similar to cap 120 inFIGS. 1A and 1B or cap 920 in FIG. 9. For clarity, cap 1620 is shown asbeing transparent in FIG. 16A, though this is not necessarily the case,and cap 1620 can be at least partially formed of an opaque material. Inthe illustrated implementation, cap 1620 can include a horizontaloptical window 1630 that forms the “top” of the cap 1620. Althoughoptical window 1630 in FIG. 16A is shown as comprising the entire top ofcap 1620, in alternative implementations optical window could compriseonly a portion of the top of cap 1620. Cap 1620 including optical window1630 defines an interior volume sized and dimensioned to receive theplurality of laser diodes 1610 a, 1610 b, 1610 c, 1610 d, and theoptical director element 1618. Cap 1620 is bonded to the base substrate1602 to provide a hermetic or partially hermetic seal between theinterior volume of the cap 1620 and a volume exterior to the cap 1620.The optical director element 1618 is positioned and oriented to direct(e.g., reflect) laser light received from each of the plurality of laserdiodes 1610 a, 1610 b, 1610 c, and 1610 d upward toward the opticalwindow 1630 of the cap 1620, wherein the laser light exits the interiorvolume, similar to FIGS. 1A and 1B.

The cap 1620 may have a round shape, rectangular shape, or other shape,similarly to as described regarding FIGS. 1A and 1B above. The opticalwindow 1630 may comprise an entire top of the cap 1620, or may compriseonly a portion thereof. In alternative implementations, optical window1630 could be positioned on a side of cap 1620 to allow beams of lightfrom laser diodes 1610 a, 1610 b, 1610 c, and 1610 d to exit the capthrough a side portion thereof. In such an implementation, each of laserdiodes 1610 a, 1610 b, 1610 c, and 1610 d can be a side-emitting laser,and optical engine 1600 a may not include optical redirector element1618.

In at least some implementations, the cap 1620 may include a pluralityof optical windows instead of a single optical window.

The optical engine 1600 a can also include four collimation/pointinglenses similarly to as discussed regarding FIGS. 1A and 1B above. Eachof the collimation lenses can be operative to receive laser light from arespective one of the laser diodes 1610 a, 1610 b, 1610 c, or 1610 d,and to generate a single color beam.

The optical engine 1600 a may also include, or may be positionedproximate to, a beam combiner that is positioned and oriented to combinethe light beams received from each of the collimation lenses or laserdiodes 1610 a, 1610 b, 1610 c, or 1610 d into a single aggregate beam.As an example, the beam combiner may include one or more diffractiveoptical elements (DOE) and/or one or more refractive/reflective opticalelements that combine the different color beams in order to achievecoaxial superposition. Exemplary beam combiners are shown and discussedwith reference to FIG. 3, 7, 9, 12A, 12B, or 13.

In at least some implementations, the laser diodes 1610 a, 1610 b, 1610c, 1610 d, the optical director element 1618, and/or the collimationlenses may be positioned differently. As noted above, laser diode drivercircuit 1614 may be mounted on a top surface or a bottom surface of thebase substrate 1602, depending on the RF design and other constraints(e.g., package size). In at least some implementations, the opticalengine 1600 a may not include the optical director element 1618, and thelaser light may be directed from the laser diodes 1610 a, 1610 b, 1610c, and 1610 d toward collimation lenses without requiring anintermediate optical director element. Additionally, in at least someimplementations, one or more of the laser diodes may be mountedindirectly on the base substrate 1602 with a submount.

Optical engine 1600 a in FIG. 16A also includes an electricallyinsulating cover 1640. In FIG. 16A, laser diodes 1610 a, 1610 b, 1610 c,and 1610 d are each connected to laser diode driver circuitry 1614 by arespective electrical connection 1616 a, 1616 b, 1616 c, or 1616 dpositioned as described above with regards to act 508 in FIG. 5.Electrical connections 1616 a, 1616 b, 1616 c, and 1616 d run across asurface of the base substrate 1602. As described above with regards toact 510 in FIG. 5, electrically insulating cover 1640 is placed,adhered, formed, or otherwise positioned over electrical connections1616 a, 1616 b, 1616 c, and 1616 d, such that each of the electricalconnections 1616 a, 1616 b, 1616 c, and 1616 d run through electricallyinsulating cover 1640. Also as described above with regards to act 510in FIG. 5, cap 1620 is placed, adhered, formed, or otherwise positionedover electrically insulating cover 1640, such that cap 1620 does notcontact any of the electrical connections 1616 a, 1616 b, 1616 c, or1616 d. For clarity, cap 1620 is shown as being transparent in FIG. 16A,though this is not necessarily the case, and cap 1620 can be at leastpartially formed of an opaque material. Electrically insulating cover1640 can be formed of a material with low electrical permittivity suchas a ceramic, such that electrical signals which run through electricalconnections 1616 a, 1616 b, 1616 c, and 1616 d do not run into orthrough electrically insulating cover 1640. In this way, electricalsignals which run through electrical connections 1616 a, 1616 b, 1616 c,and 1616 d can be prevented from running into or through cap 1620, whichcan be formed of an electrically conductive material. Although FIG. 16Ashows electrically insulating cover 1640 as extending along only part ofa side of cap 1620, one skilled in the art will appreciate thatelectrically insulating cover 1640 can extend along an entire sidelength of cap 1620.

One skilled in the art will appreciate that the positions of laser diodedriver circuitry 1614, electrical connections 1616 a, 1616 b, 1616 c,1616 d, and electrically insulating cover 1640 as shown in FIG. 16Acould also be applied in other implementations of the subject systems,devices and methods. For example, in the implementations of FIGS. 1A and1B, laser diode driver circuitry 114 could be positioned on top surface104 of base substrate 102, and electrical connections 116 could runacross top surface 104 under an electrically insulating cover, such thatelectrical connections 116 do not contact any conductive portion of cap120.

FIG. 16B is an isometric view an optical engine 1600 b similar in atleast some respects to optical engine 1600 a of FIG. 16A. One skilled inthe art will appreciate that the description of optical engine 1600 a inFIG. 16A is applicable to optical engine 1600 b in FIG. 16B, unlesscontext clearly dictates otherwise. The optical engine 1600 b includes abase substrate 1603 a. Similar to base substrate 1602 in FIG. 16A, basesubstrate 1603 a may be formed from a material that is radio frequency(RF) compatible and is suitable for hermetic sealing. For example, thebase substrate 1603 a may be formed from low temperature co-firedceramic (LTCC), alumina, Kovar®, etc.

One difference between optical engine 1600 b in FIG. 16B and opticalengine 1600 a in FIG. 16A relates to what components are bonded (e.g.attached) to base substrate 1603 a. In optical engine 1600 b, each of:laser diodes 1610 a, 1610 b, 1610 c, 1610 d; cap 1620; electricalconnections 1616 a, 1616 b, 1616 c, 1616 d; and electrically insulatingcover 1640 are bonded (e.g., attached) to base substrate 1603 a.However, laser diode driver circuit 1614 is not necessarily bondeddirectly to base substrate 1603 a. Instead, laser diode driver circuit1614 could be bonded to a separate base substrate 1603 b. Similar tobase substrate 1602 in FIG. 16A and base substrate 1603 a in FIG. 16B,base substrate 1603 b may be formed from a material that is radiofrequency (RF) compatible and is suitable for hermetic sealing. Forexample, the base substrate 1603 b may be formed from low temperatureco-fired ceramic (LTCC), alumina, Kovar®, etc. In an alternativeimplementation, laser diode drive circuit 1614 may not need to be bondedto a substrate at all, and could simply be mounted directly to a frameof a WHUD.

For implementations where laser diode drive circuit 1614 is not bondedto base substrate 1603 a, electrical contacts 1617 a, 1617 b, 1617 c,and 1617 d could be bonded to base substrate 1603 a, each at an end of arespective electrical connection 1616 a, 1616 b, 1616 c, or 1616 d asdescribed above with regards to act 508 in FIG. 5. In this way,electrical contacts 1617 a, 1617 b, 1617 c, and 1617 d could be used toelectrically couple laser diode drive circuit 1614 to electricalconnections 1616 a, 1616 b, 1616 c, and 1616 d and consequently laserdiodes 1610 a, 1610 b, 1610 c, and 1610 d.

Although the implementations of FIGS. 16A and 16B illustrate exampleswhich include cap 1620, cap 1620 could be replaced by a waveguide andsealing medium similar to as described with reference to FIG. 15.

For example, a waveguide and sealing medium could be disposed on basesubstrate 1602 in FIG. 16A to cover the plurality of laser diodes 1610a, 1610 b, 1610 c, and 1610 d; optical director element 1618 (ifincluded); and at least a portion or all of electrical connections 1616a, 1616 b, 1616 c, and 1616 d. Laser diode driver circuitry 1614 couldoptionally be covered as well, or left uncovered. In this way,electrical connections 1616 a, 1616 b, 1616 c, and 1616 d will connectlaser diode circuitry 1614 to laser diodes 1610 a, 1610 b, 1610 c, and1610 d through the waveguide and sealing medium.

As another example, a waveguide and sealing medium could be disposed onbase substrate 1603 a in FIG. 16B to cover the plurality of laser diodes1610 a, 1610 b, 1610 c, and 1610 d; optical director element 1618 (ifincluded); and a portion of electrical connections 1616 a, 1616 b, 1616c, and 1616 d. Electrical contacts 1617 a, 1617 b, 1617 c, and 1617 dcould be left uncovered, such that laser diode circuitry 1614 can becoupled thereto. In this way, electrical connections 1616 a, 1616 b,1616 c, and 1616 d will connect laser diode circuitry 1614 to laserdiodes 1610 a, 1610 b, 1610 c, and 1610 d via electrical contacts 1617a, 1617 b, 1617 c, and 1617 d, through the waveguide and sealing medium.

FIG. 17A is a left side sectional elevational view of an optical engine1700. FIG. 17B is a front side elevational view of the optical engine1700. The optical engine 1700 includes several components that may besimilar or identical to the components of the optical engines discussedabove. Thus, some or all of the discussion above may be applicable tothe optical engine 1700.

The optical engine 1700 includes a base substrate 1702 having a topsurface 1704 and a bottom surface 1706 opposite the top surface. Thebase substrate 1702 may be formed from a material that is radiofrequency (RF) compatible and is suitable for hermetic sealing. Forexample, the base substrate 1702 may be formed from low temperatureco-fired ceramic (LTCC), aluminum nitride (AlN), alumina, etc.

The optical engine 1700 also includes a plurality of chip submounts 1708(four chip submounts 1708 a-1708 d shown in FIG. 17B) that are bonded(e.g., attached) to the top surface 1704 of the base substrate 1702. Theplurality of chip submounts 1708 are aligned in a row across a width ofthe optical engine 1700 between the left and right sides thereof. Eachof the plurality of chip submounts 1708 includes a laser diode 1710,also referred to as a laser chip or laser die, bonded thereto. Inparticular, an infrared chip submount 1708 a carries an infrared laserdiode, a red chip submount 1708 b carries a red laser diode, a greenchip submount 1708 c carries a green laser diode, and a blue chipsubmount 1708 d carries a blue laser diode. In operation, the infraredlaser diode provides infrared laser light, the red laser diode providesred laser light, the green laser diode provides green laser light, andthe blue laser diode provides blue laser light. Each of the laser diodes1710 may comprise one of an edge emitter laser or a vertical-cavitysurface-emitting laser (VCSEL), for example. Each of the four laserdiode/chip submount pairs may be referred to collectively as a “laserchip on submount,” or a laser CoS 1712. Thus, the optical engine 1700includes an infrared laser CoS, a red laser CoS, a green laser CoS, anda blue laser CoS. In at least some implementations, one or more of thelaser diodes 1710 may be bonded directly to the base substrate 1702without use of a submount 1708.

The optical engine 1700 also includes a laser diode driver circuit 1714bonded to the bottom surface 1706 of the base substrate 1702. The laserdiode driver circuit 1714 is operatively coupled to the plurality oflaser diodes 1710 via suitable electrical connections 1716 toselectively drive current to the plurality of laser diodes. Generally,the laser diode driver circuit 1714 may be positioned relative to theCoSs 1712 to minimize the distance between the laser diode drivercircuit 1714 and the CoSs 1712. Although not shown in FIG. 17, the laserdiode driver circuit 1714 may be operatively coupleable to a controller(e.g., microcontroller, microprocessor, ASIC) that controls theoperation of the laser diode driver circuit 1714 to selectively modulatelaser light emitted by the laser diodes 1710. In at least someimplementations, the laser diode driver circuit 1714 may be bonded toanother portion of the base substrate 1702, such as the top surface 1704of the base substrate, similar to the implementation shown in FIG. 16A.In at least some implementations, the laser diode driver circuitry 1714may be remotely located and operatively coupled to the laser diodes1710, similar to the implementation shown in FIG. 16B. For example, thelaser diode driver circuitry 1714 may be bonded to another substrateseparate from base substrate 1702, or may be mounted directly to a frameor support structure of a WHUD in which the optical engine 1700 isimplemented. The electrical connections 1616 a-1616 d, electricalcontacts 1617 a-1617 d, and electrically insulating cover 1640 of FIGS.16A and 16B could also be implemented in optical engine 1700 shown inFIGS. 17A and 17B. In order to not require the use of impedance matchedtransmission lines, the size scale may be small compared to a wavelength(e.g., lumped element regime), where the electrical characteristics aredescribed by (lumped) elements like resistance, inductance, andcapacitance.

The optical engine 1700 also includes a cap 1720 that includes avertical sidewall 1722 and a horizontal wall or top portion 1725. Thevertical sidewall 1722 includes a lower first end 1724 and an uppersecond end 1726 opposite the first end. A flange 1728 may be disposedaround a perimeter of the sidewall 1722 adjacent the lower first end1724. Within a portion of the vertical sidewall 1722 there is an opticalwindow 1730 positioned proximate the laser diodes 1710 to pass lighttherefrom out of the cap 1720. The sidewall 1722 and the optical window1730 together define an interior volume 1732 sized and dimensioned toreceive the plurality of chip submounts 1708 and the plurality of laserdiodes 1710. The lower first end 1724 and the flange 1728 of the cap1720 are bonded to the base substrate 1702 to provide a hermetic sealbetween the interior volume 1732 of the cap and a volume 1734 exteriorto the cap.

The cap 1720 may have a round shape, rectangular shape, or other shape.Thus, the vertical sidewall 1722 may comprise a continuously curvedsidewall, a plurality (e.g., four) of adjacent planar portions, etc. Theoptical window 1730 may comprise an entire side of the cap 1720, or maycomprise only a portion thereof. In at least some implementations, thecap 1720 may include a plurality of optical windows (e.g., four opticalwindows, one for each of the laser diodes 1710) instead of a singleoptical window 1730.

The optical engine 1700 also includes four collimation/pointing lenses1736, one for each of the four laser diodes 1710 that are bonded to thetop surface 1704 of the base substrate 1702 in a row. Each of theplurality of collimations lenses 1736 may be positioned and oriented toreceive light from a corresponding one of the laser diodes 1710 and todirect collimated light through the optical window 1730. In at leastsome implementations, the collimation lenses 1736 may comprise onemicro-optic lens array that is passively aligned and bonded inside thehermetic housing provided by the cap 1720. In at least someimplementations, the collimation lenses 1736 may be positioned outsideof the cap 1720 and may receive light from the laser diodes 1710 via theoptical window 1730.

The collimations lenses 1736 couple the collimated beams of light towarda diffractive grating waveguide combiner 1750 which combines the lightto provide a superimposed collimated beam 1756 (FIG. 17A). In theillustrated implementation, the grating waveguide combiner 1750 includestwo waveguides 1750 a and 1750 b stacked proximate each other (e.g.,with or without space therebetween), but in other implementations adifferent number (e.g., four) of waveguides may be used, depending onthe particular design. The waveguides 1750 a and 1750 b may be bonded tothe top surface 1704 of the base substrate 1702 or otherwise positionedproximate the optical window 1730 to receive the collimated beams oflight from the collimation lenses 1736.

In the illustrated implementation, the grating waveguide combiner 1750includes four input grating couplers 1752 a-1752 d which receive acollimated light beam from the collimation lenses 1736 a-1736 d,respectively, and an output grating coupler 1754 that outputs thesuperimposed collimated beam 1756 (FIG. 17A). As an example, thewaveguide 1750 a may include input grating couplers 1752 a and 1752 bfor receiving infrared light and red light, respectively, and thewaveguide 1750 b may include input grating couplers 1752 c and 1752 dfor receiving green light and blue light, respectively. In this example,the waveguide 1750 a may pass or otherwise direct the red light andgreen light to the waveguide 1750 b.

The output grating coupler 1754 may be disposed on a surface of thewaveguide 1750 b facing away from the optical window 1730 to output thesuperimposed collimated light 1756 to another component (e.g., one ormore diffractive optical elements) of the optical engine 1700 or to alaser projector of which the optical engine is a part. For example,following out-coupling of the aggregate beam 1756 from the outputgrating 1754 of the waveguide 1750 b, the aggregated beam may becollimated via a common collimation lens (e.g., lens 802 of FIGS. 8 and9). In at least some implementations, the collimation lens may be eitheran achromatic lens or an apochromatic lens (or lens assemblies),depending on the particular optical design and tolerances of the system.In at least some implementations, one or more diffractive opticalelements (e.g., diffractive optical elements 804 of FIGS. 8 and 9) maybe used to provide wavelength dependent focus correction or otherfunctionality.

Waveguide combiner 1750, input grating couplers 1752 a-1752 d, andoutput grating coupler 1754 can be formed and positioned using anyappropriate method. As one example, waveguide combiner 1750, inputgrating couplers 1752 a-1752 d, and output grating coupler 1754 can beformed using the technique described with reference to FIGS. 10 and 11.In particular, waveguide combiner 1750, input grating couplers 1752a-1752 d, and output grating coupler 1754 could be written in writeableglass and/or waveguide medium user a laser writing assembly, andsubsequently positioned on base substrate 1702. As another example,writeable glass and/or waveguide medium could be positioned on basesubstrate, and waveguide combiner 1750, input grating couplers 1752a-1752 d, and output grating coupler 1754 can subsequently be directlylaser written therein, such as by using similar techniques to thosedescribed with reference to FIGS. 12A, 12B, 13, 14 and 15.

Throughout this application, collimation lenses have been represented inthe Figures by a simple curved lens shape. However, the subject systems,devices, and methods can utilize more advanced collimation schemes, asappropriate for a given application.

FIG. 18 shows an exemplary situation where using an advanced collimationscheme would be helpful. FIG. 18 is an isometric view of a laser diode1800. The laser diode 1800 may be similar or identical to the variouslaser diodes discussed herein. The laser diode 1800 outputs a laserlight beam 1802 via an output facet 1804 of the laser diode. FIG. 18shows the divergence of the light 1802 emitting from the laser diode1800. As shown, the light beam 1802 may diverge by a substantial amountalong a fast axis 1806 (or perpendicular axis) and by a lesser amount inthe slow axis 1808 (parallel axis). As a non-limiting example, in atleast some implementations, the light beam 1802 may diverge with fullwidth half maximum (FWHM) angles of up to 40 degrees in the fast axisdirection 1806 and up to 10 degrees in the slow axis direction 1808.This divergence results in a rapidly expanding elliptical cone.

FIGS. 19A and 19B show an exemplary collimation scheme that can be usedto circularize and collimate an elliptical beam such as that shown inFIG. 18. FIG. 19A illustrates an orthogonal view of the fast axis 1806of light beam 1802 emitted from laser diode 1800. FIG. 19B illustratesan orthogonal view of the slow axis 1808 of light beam 1802 emitted fromlaser diode 1800. As shown in FIG. 19A, a first lens 1900 collimateslight beam 1802 along fast axis 1806. As shown in FIG. 19B, first lens1900 is shaped so as to not substantially influence light beam 1802along slow axis 1808. Subsequently, as shown in FIG. 19B, light beam1802 is collimated along slow axis 1808 by a second lens 1902. As shownin FIG. 19A, second lens 1902 is shaped so as to not substantiallyinfluence light beam 1802 along fast axis 1806. In essence, light beam1802 is collimated along fast axis 1806 separately from slow axis 1808.By collimating light beam 1802 along fast axis 1806 separately from slowaxis 1808, the collimation power applied to each axis can beindependently controlled by controlling the power of lens 1900 and lens1902 separately. Further, spacing between each of laser diode 1800, lens1900, and lens 1902 can be controlled to collimate light beam 1802 to acertain width in each axis separately. If light beam 1802 is collimatedalong fast axis 1806 to the same width as slow axis 1808, light beam1802 can be circularized. Because light beam 1802 will typically divergefaster in the fast axis 1806, it is generally preferable to collimatelight beam 1802 along fast axis 1806 first, then collimate light beam1802 along slow axis 1808 after. However, it is possible in certainapplications to collimate light beam 1802 along slow axis 1808 first,and subsequently collimate light beam 1802 along fast axis 1806 after.This can be achieved by reversing the order of first lens 1900 withsecond lens 1902, with respect to the path of travel of light beam 1802.

FIGS. 19C and 19D are isometric views which illustrate exemplary shapesfor lenses 1900 and 1902. Each of lens 1900 and 1902 can be for examplea half-cylinder as in FIG. 19C, a full cylinder as in FIG. 19D, aquarter cylinder, a three-quarter cylinder, any other partial cylinder,or any other appropriate shape. Lenses 1900 and 1902 can be similarlyshaped, or can have different shapes.

FIGS. 20A and 20B illustrate an alternative collimation scheme. FIG. 20Aillustrates an orthogonal view of the fast axis 1806 of light beam 1802emitted from laser diode 1800. FIG. 20B illustrates an orthogonal viewof the slow axis 1808 of light beam 1802 emitted from laser diode 1800.As shown in FIG. 20A, a first lens 2000 redirects light beam 1802 alongfast axis 1806, to reduce divergence of light beam 1802 along fast axis1806. As shown in FIG. 20B, first lens 2000 is shaped so as to notsubstantially influence light beam 1802 along slow axis 1808.Preferably, first lens 2000 will reduce divergence of light beam 1802along fast axis 1806 to match divergence of light beam 1802 along slowaxis 1808. That is, first lens 2000 preferably circularizes light beam1802. Subsequently, as shown in FIGS. 20A and 20B, light beam 1802 iscollimated along both fast axis 1806 and slow axis 1808 by a second lens2002. As shown in FIGS. 20A and 20B, second lens 2002 is shapedsimilarly with respect to both the fast axis 1806 and the slow axis1808, to evenly collimate light beam 1802. In essence, first lens 2000circularizes light beam 1802, and subsequently second lens 2002collimates light beam 1802 along both axes. First lens 2000 can forexample be shaped similarly to lens 1900 or lens 1902 discussed above,and shown in FIGS. 19C and 19D. Second lens 2002 can for example beshaped as a double convex lens as illustrated in FIG. 20C, or a singleconvex lens (convex on either side) as illustrated in FIG. 20D, or anyother appropriate shape of collimating lens.

The collimation schemes illustrated in FIGS. 19A-19D and 20A-20D, anddiscussed above could be used in place of any of the collimation lensesdescribed herein, including at least collimation lenses 136 a, 136 b,136 c, 136 d.

A person of skill in the art will appreciate that the teachings of thepresent systems, methods, and devices may be modified and/or applied inadditional applications beyond the specific WHUD implementationsdescribed herein. In some implementations, one or more optical fiber(s)may be used to guide light signals along some of the paths illustratedherein.

The WHUDs described herein may include one or more sensor(s) (e.g.,microphone, camera, thermometer, compass, altimeter, and/or others) forcollecting data from the user's environment. For example, one or morecamera(s) may be used to provide feedback to the processor of the WHUDand influence where on the display(s) any given image should bedisplayed.

The WHUDs described herein may include one or more on-board powersources (e.g., one or more battery(ies)), a wireless transceiver forsending/receiving wireless communications, and/or a tethered connectorport for coupling to a computer and/or charging the one or more on-boardpower source(s).

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other portable and/or wearableelectronic devices, not necessarily the exemplary wearable electronicdevices generally described above.

For instance, the foregoing detailed description has set forth variousembodiments of the devices and/or processes via the use of blockdiagrams, schematics, and examples. Insofar as such block diagrams,schematics, and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such block diagrams, flowcharts, orexamples can be implemented, individually and/or collectively, by a widerange of hardware, software, firmware, or virtually any combinationthereof. In one embodiment, the present subject matter may beimplemented via Application Specific Integrated Circuits (ASICs).However, those skilled in the art will recognize that the embodimentsdisclosed herein, in whole or in part, can be equivalently implementedin standard integrated circuits, as one or more computer programsexecuted by one or more computers (e.g., as one or more programs runningon one or more computer systems), as one or more programs executed by onone or more controllers (e.g., microcontrollers) as one or more programsexecuted by one or more processors (e.g., microprocessors, centralprocessing units, graphical processing units), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of ordinary skill in the art in light of theteachings of this disclosure.

When logic is implemented as software and stored in memory, logic orinformation can be stored on any processor-readable medium for use by orin connection with any processor-related system or method. In thecontext of this disclosure, a memory is a processor-readable medium thatis an electronic, magnetic, optical, or other physical device or meansthat contains or stores a computer and/or processor program. Logicand/or the information can be embodied in any processor-readable mediumfor use by or in connection with an instruction execution system,apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions associated with logic and/or information.

In the context of this specification, a “non-transitoryprocessor-readable medium” can be any element that can store the programassociated with logic and/or information for use by or in connectionwith the instruction execution system, apparatus, and/or device. Theprocessor-readable medium can be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus or device. More specific examples (anon-exhaustive list) of the computer readable medium would include thefollowing: a portable computer diskette (magnetic, compact flash card,secure digital, or the like), a random access memory (RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM, EEPROM,or Flash memory), a portable compact disc read-only memory (CDROM),digital tape, and other non-transitory media.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, at least the followingare incorporated herein by reference in their entirety: U.S. ProvisionalPatent Application Ser. No. 62/438,725, U.S. Non-Provisional PatentApplication Ser. No. 15/848,265 (U.S. Publication Number 2018/0180885),U.S. Non-Provisional patent application Ser. No. 15/848,388 (U.S.Publication Number 2018/0180886), U.S. Provisional Patent ApplicationSer. No. 62/450,218, U.S. Non-Provisional Patent Application Ser. No.15/852,188 (U.S. Publication Number 2018/0210215), U.S. Non-Provisionalpatent application Ser. No. 15/852,282, (U.S. Publication Number2018/0210213), U.S. Non-Provisional patent application Ser. No.15/852,205 (U.S. Publication Number 2018/0210216), U.S. ProvisionalPatent Application Ser. No. 62/575,677, U.S. Provisional PatentApplication Ser. No. 62/591,550, U.S. Provisional Patent ApplicationSer. No. 62/597,294, U.S. Provisional Patent Application Ser. No.62/608,749, U.S. Provisional Patent Application Ser. No. 62/609,870,U.S. Provisional Patent Application Ser. No. 62/591,030, U.S.Provisional Patent Application Ser. No. 62/620,600, U.S. ProvisionalPatent Application Ser. No. 62/576,962, U.S. Provisional PatentApplication Ser. No. 62/760,835, U.S. Non-Provisional patent applicationSer. No. 16/201,664, U.S. Non-Provisional patent application Ser. No.16/168,690, U.S Non-Provisional patent application Ser. No. 16/171,206,U.S Non-Provisional Patent Application Ser. No. 16/203,221, U.SNon-Provisional patent application Ser. No. 16/216,899, U.SNon-Provisional patent application Ser. No. 16/231,019, and/or PCTPatent Application PCT/CA2018051344. Aspects of the embodiments can bemodified, if necessary, to employ systems, circuits and concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A laser projector, comprising: an optical engine, comprising: a basesubstrate; a plurality of laser diodes, each of the plurality of laserdiodes bonded directly or indirectly to the base substrate; at least onelaser diode driver circuit operatively coupled to the plurality of laserdiodes to selectively drive current to the plurality of laser diodes; aplurality of collimation lenses, each of the plurality of collimationlenses positioned proximate a respective one of the plurality of laserdiodes collimates light emitted therefrom; a cap comprising at least onewall and at least one optical window that, together with the basesubstrate, define an interior volume sized and dimensioned to receive atleast the plurality of laser diodes and the plurality of collimationlenses, the cap being bonded to the base substrate to provide a hermeticor partially hermetic seal between the interior volume of the cap and avolume exterior to the cap, and the optical window positioned andoriented to allow beams of light emitted from the plurality of laserdiodes through the collimation lenses to exit the interior volume; and agrating waveguide combiner positioned proximate the optical window ofthe cap, the grating waveguide combiner comprising a plurality of inputgrating couplers and at least one output grating coupler, in operation,the grating waveguide combiner receives a plurality of beams of light atthe respective plurality of input grating couplers and combines theplurality of beams of light to provide a collimated aggregated beam oflight at the output grating coupler; and at least one scan mirrorpositioned to receive the aggregate beam of light output at the outputgrating coupler of the grating waveguide combiner, the at least one scanmirror controllably orientable to redirect the aggregate beam of lightover a range of angles.
 2. The laser projector of claim 1 wherein thegrating waveguide combiner comprises a first grating waveguide and asecond grating waveguide.
 3. The laser projector of claim 2 wherein eachof the first and second grating waveguides includes at least two inputgrating couplers.
 4. The laser projector of claim 1 wherein the gratingwaveguide combiner comprises at least four waveguides.
 5. The laserprojector of claim 1 wherein the plurality of collimation lenses areformed as a micro-optic lens array.
 6. The laser projector of claim 1wherein the plurality of collimation lenses are bonded to the basesubstrate.
 7. The laser projector of claim 1 wherein the gratingwaveguide combiner is bonded to the base substrate proximate the opticalwindow of the cap.
 8. The laser projector of claim 1, the optical enginefurther comprising: a common collimation lens positioned and oriented toreceive and collimate the aggregate beam of light from the outputgrating coupler of the grating waveguide combiner.
 9. The laserprojector of claim 8 wherein the common collimation lens comprises anachromatic lens.
 10. The laser projector of claim 8 wherein the commoncollimation lens comprises an apochromatic lens.
 11. The laser projectorof claim 1, the optical engine further comprising at least onediffractive optical element positioned and oriented to receive theaggregate beam of light, in operation, the at least one diffractiveoptical element provides wavelength dependent focus correction for theaggregate beam of light.
 12. The laser projector of claim 1, the opticalengine further comprising: a plurality of chip submounts bonded to thebase substrate, wherein each of the laser diodes are bonded to acorresponding one of the plurality of chip submounts.
 13. The laserprojector of claim 1 wherein the plurality of laser diodes includes ared laser diode to provide a red laser light, a green laser diode toprovide a green laser light, a blue laser diode to provide a blue laserlight, and an infrared laser diode to provide infrared laser light. 14.The laser projector of claim 1 wherein the base substrate is formed fromat least one of low temperature co-fired ceramic (LTCC), aluminumnitride (AlN), or alumina.
 15. The laser projector of claim 1 whereinthe at least one laser diode driver circuit is bonded to a first surfaceof the base substrate, and the plurality of laser diodes and the cap arebonded to a second surface of the base substrate, the second surface ofthe base substrate opposite the first surface of the base substrate. 16.The laser projector of claim 1 wherein the at least one laser diodedriver circuit, the plurality of laser diodes, and the cap are bonded toa first surface of the base substrate.
 17. The laser projector of claim1 wherein the plurality of laser diodes and the cap are bonded to thebase substrate, and the at least one laser diode driver circuit isbonded to another substrate separate from the base substrate.
 18. Thelaser projector of claim 1 wherein each of the laser diodes comprisesone of an edge emitter laser or a vertical-cavity surface-emitting laser(VCSEL).